UNIVERSITY  OF  CALIFORNIA   PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 
BERKELEY,  CALIFORNIA 


FUNGICIDAL  DUSTS  FOR  THE  CONTROL  OF  BUNT 


BY 

WILLIAM  W.  MACKIE  and  FRED  N.  BR1GGS 


(Based  on  investigations  conducted  under  cooperative  agreement, 
between  the  Office  of  Cereal  Investigations,  of  the  Bureau  of  Plant 
Industry,  United  States  Department  of  Agriculture,  and  the  Univer 
sity  of  California  Agricultural  Experiment  Station.) 


BULLETIN  No.  364 

Berkeley,  California,  May,  1923 


UNIVERSITY  OF  CALIFORNIA  PRESS 

BERKELEY 

1923 


David  P.  Barrows,  President  of  the  University. 

EXPERIMENT  STATION  STAFF 
HEADS  OF  DIVISIONS 

Thomas  Forsyth  Hunt,  Dean. 

Edward  J.  Wickson,  Horticulture  (Emeritus). 

,  Director  of  Eesident  Instruction. 

C.  M.  Haring,  Veterinary  Science,  Director  of  Agricultural  Experiment  Station. 

B.  H.  Crocheron,  Director  of  Agricultural  Extension. 

C.  B.  Hutchison,  Plant  Breeding,  Director  of  the  Branch  of  the  College  of 

Agriculture  at  Davis. 
H.  J.  Webber,  Sub-tropical  Horticulture,  Director  of  Citrus  Experiment  Station. 
William  A.  Setchell,  Botany. 
Myer  E.  Jaffa,  Nutrition. 
Ralph  E.  Smith,  Plant  Pathology. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 
John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Fruit  Products. 
Warren  "T.  Clarke,  Agricultural  Extension. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
Walter  Mulford,  Forestry. 
James  T.  Barrett,  Plant  Pathology. 
W.  P.  Kelley,  Agricultural  Chemistry. 
H.  J.  Quayle,  Entomology 
Elwood  Mead,  Rural  Institutions. 
H.  S.  Reed,  Plant  Physiology. 
L.  D.  Batchelor,  Orchard  Management. 
W.  L.  Howard,  Pomology. 
"Frank  Adams,  Irrigation  Investigations. 

C.  L.  Roadhouse,  Dairy  Industry. 
R.  L.  Adams,  Farm  Management. 

W.  B.  Herms,  Entomology  and  Parasitology. 
John  E.  Dougherty,  Poultry  Husbandry. 

D.  R.  Hoagland,  Plant  Nutrition. 
G.  H.  Hart,  Veterinary  Science. 

L.  J.  Fletcher,  Agricultural  Engineering. 
Edwin  C.  Voorhies,  Assistant  to  the  Dean. 

DIVISION  OF  AGRONOMY 

J.  W.  Gilmore  B.  A.  Madson 

P.  B.  Kennedy  J.  F.  Duggar 

G.  W.  Hendry  J.  P.  Conrad 
W.  W.  Mackie 


*  la  cooperation  with  Division  of  Agricultural  Engineering,  Bureau  of  Public  Roads,  U.  8. 
Department  of  Agriculture. 


FUNGICIDAL  DUSTS  FOR  THE  CONTROL  OF  BUNT 

By  WILLIAM  W.  MACKIE  and  FRED  N.  BRIGGS 


CONTENTS 

PAGE 

Fungicidal  dusts  for  the  control  of  bunt  or  stinking  smut  of  wheat 533 

Early  experiments  with  chemical  dusts  for  the  control  of  bunt 536 

Plan  of  procedure 537 

Influence  of  spore  load  upon  bunt  attack 539 

Control  of  bunt  by  solutions  of  standard  fungicides 540 

Effect  of  flowers  of  sulfur  on  bunt  control 540 

Control  of  bunt  by  copper  sulfate  powder 543 

Copper  sulfate  dust  as  a  substitute  for  copper  corbonate 545 

Miscellaneous  chemical  dusts 545 

Effect  of  copper  carbonate  dust  on  control  of  bunt 545 

Effect  of  dilution  of  copper  carbonate  on  bunt  control 548 

Comparative  effectiveness  of  some  commercial  samples  of  copper  carbonate 549 

Effect  of  fungicidal  dusts  upon  seed  germination 551 

Stimulation  of  wheat  seedlings  by  copper  carbonate  dust 553 

Standards  of  chemical  purity  and  physical  fineness  for  copper  carbonate  dust 554 

Suggested  qualities  for  a  standard  copper  carbonate 557 

Machines  for  applying  copper  carbonate  dust 560 

Effect  of  copper  carbonate  dust  upon  operators 563 

Demonstrations  with  copper  carbonate  dust  on  farms 563 

Sources  of  copper  carbonate 566 

Summary 567 


FUNGICIDAL  DUSTS  FOR  THE  CONTROL  OF  BUNT  OR 
STINKING  SMUT  OF  WHEAT 

Bunt,  or  stinking  smut,  has  long  been  recognized  as  a  destructive 
disease  of  wheat.  Its  control,  however,  was  not  undertaken  in  a 
scientific  or  effective  manner  until  about  the  middle  of  the  last  century, 
when  Kuhn18  began  his  classic  experiments  on  the  effect  of  copper 
sulfate  on  the  spores  of  the  bunt  fungus.  Although  effective  remedies 
for  control  of  bunt  have  been  found  in  the  use  of  bluestone  (copper 
sulfate  and  formaldehyde),  their  universal  application  has  not  been 
practiced  for  the  following  reasons: 

1.  Bluestone  solutions  of  sufficient  strength  to  destroy  the  bunt 
spores  kills  the  wheat  germ,  or  so  affects  it  that  the  growth  of  the 
primary  roots  are  delayed  or  the  plumule  is  distorted  and  weakened. 


534  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Forty  to  60  per  cent  of  the  wheat  treated  by  bluestone  on  our  Cali- 
fornia farms  never  comes  up.  Solutions  which  do  not  injure  the  germ 
are  too  weak  to  prevent  bunt  infection. 

2.  The  dipping  of  bluestone-treated  wheat  in  a  lime  solution  pre- 
vents the  greater  portion  of  the  bluestone  injury,  but  has  the  dis- 


Fig.  1. — No.  5,  bunted  White  Australian  head  and  bunt  gall.  No.  6,  normal 
White  Australian  head  and  kernel.  Natural  size.  Under  competitive  field  con- 
ditions bunt  attack  reduces  the  size  of  the  plant,  head  and  kernel. 

advantages  of  extra  cost  in  labor  and  time.  The  additional  costs 
could  be  borne  if  this  were  all,  but  frequently  heavy  losses  of  seed 
treated  by  the  bluestone-lime  method  have  occurred  when  such  seed 
has  been  stored  too  wet.  When  seed  is  properly  dried,  as  usually  is 
the  case  with  seed  treated  early  in  the  fall  before  the  rainy  season 


BULLETIN    364]         FUNGICIDAL   DUSTS   FOR   THE    CONTROL    OF   BUNT 


535 


is  far  advanced,  no  injury  from  heating  or  fermentation  occurs. 
But  when  weather  conditions  force  the  farmer  to  store  seed  too  wet, 
the  lime  coating  prevents  proper  drying,  and  seed  losses  may  follow. 
3.  Formaldehyde  is  an  effective  remedy  against  infection  from 
seed-borne  spores  of  the  bunt  fungus  and  several  other  smuts  of 
cereals,  but  it,  too,  is  limited  by  its  destruction  of  seed  germs  under 
certain  climatic  conditions,  as  has  been  conclusively  shown  by  investi- 


ng. 2. — Eoot  development  retarded  by  bluestone.  Normal  seedling  to  left. 
Seedlings  with  delayed  root  development  frequently  die.  In  others,  delayed 
growth  and  maturity  result. 


gations  in  California.17' 21  The  experience  of  farmers  in  California 
and  other  semi-arid  regions6  positively  shows  that  seed  injury  results 
from  formaldehyde-treated  seed  either  when  stored  dry  for  a  period 
of  more  than  48  hours  before  seeding  or  when  seeded  into  soil  too 
dry  to  cause  immediate  germination.  This  injury  is  seen  in  destroyed 
germs,  distorted  plumules,  and  weakened  seedlings.  Instances  have 
been  recorded  in   California  where  thousands  of  acres  sown  with 


536  UNIVERSITY    OF    CALIFORNIA — EXPERIMENT    STATION 

formaldehyde-treated  seed  failed  to  produce  even  a  poor  stand. 
Owing;  to  the  necessity  of  California  farmers  having  to  sow  much 
of  their  summer  fallowed  lands  before  the  rainy  season  begins, 
formaldehyde  cannot  be  used  without  liability  to  severe  seed  injury. 

4.  The  loss  of  time  at  the  busy  seeding  period  tends  to  prevent 
seed  treatment.  It  has  been  shown  by  von  Tubeuf29  that  seed  from 
a  crop  with  only  one  or  two  per  cent  of  bunt  showing  no  visible  spores 
may  in  the  following  crop  produce  20  to  30  per  cent  of  smutted 
plants.  Seed  treatment,  therefore,  should  be  practiced  every  year 
whether  bunt  appears  to  be  present  or  not. 

In  order  to  induce  the  farmer  to  treat  his  seed  wheat  for  bunt 
every  year,  the  difficulties  presented  in  the  use  of  solutions  of  blue- 
stone,  bluestone  and  lime,  and  formaldehyde,  must  be  obviated.  An 
effective  fungicide,  which  can  be  applied  to  seed  long  in  advance  of 
seeding  operations,  and  which  will  not  injure  seed  germs  even  in 
the  hands  of  careless  farm  help,  must  be  provided  if  universal  con- 
trol of  bunt  is  to  be  attained.  The  copper  carbonate  dust  method 
of  seed  treatment  appears  to  meet  these  requirements.  The  results 
of  three  years'  experiments  and  tests  to  determine  the  effectiveness 
as  well  as  the  limitations  of  copper  carbonate  dust  when  applied  to 
bunt-infested  seed  are  here  presented  in  support  of  this  new  method 
of  seed  treatment. 


EARLY  EXPERIMENTS  WITH  CHEMICAL  DUSTS  FOR  THE 
CONTROL  OF  BUNT 

Farmers  always  have  desired  a  dry  fungicide  because  of  the 
difficulties  and  costs  connected  with  the  use  of  liquid  preventives. 
Lime,  either  burnt  or  air-slaked,  has  long  been  applied  as  a  powder, 
but  ineffective  control  of  bunt  has  prevented  its  acceptance.  Bolley3 
tried  many  dry  processes,  testing  among  others  "dry  powdered 
formaldehyde  mixed  with  chloride  of  lime  and  flowers  of  sulfur,  and 
suggests  that  extended  research  might  develop  a  satisfactory  dry 
method.  His  own  experiment  gave  little  or  no  bunt  control,  and 
much  seed  injury. 

Copper  carbonate  dust  as  a  smut  fungicide  was  used  by  von 
Tubeuf  in  1902, 29  who  treated  heavily  bunted  seed  with  copper  car- 
bonate dust  and  secured  only  1.7  per  cent  of  bunted  heads.  At  the 
same  time  untreated  seed  gave  29.3  per  cent,  while  Bordeaux  powder 
gave  14.9  per  cent.  No  reason  is  given  why  the  use  of  copper  car- 
bonate dust  was  not  continued.     Darnell-Smith7'  8>  9> ai  experimented 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT 


537 


with  heavily  bunt-infected  seed  at  Cowra  and  at  Wagga  in  New  South 
Wales  in  1915  and  later.  He  secured  better  results  in  bunt  control 
and  seed  germination  with  copper  carbonate  dust  (2  ounces  per 
bushel)  than  with  standard  methods.  Following  the  success  of 
Darnell-Smith,  preliminary  experiments  with  copper  carbonate  dust 
were  made  at  Berkeley  and  Davis22-  23  in  1920.  These  experiments 
were  highly  encouraging,  but  were  limited  owing  to  late  seeding 
(March  8  and  April  9).  During  the  years  1921  and  1922,  a  large 
number  of  experiments  were  conducted  at  Davis.  Care  was  taken 
to  check,  with  many  duplications,  all  dust  treatments  with  the 
standard  bluestone  and  formaldehyde  treatments.  Because  of  the 
large  number  of  experiments  conducted,  it  has  been  found  necessary 
to  present  these  results  in  averages. 


PLAN  OF  PROCEDURE 

A  method  of  seed  treatment  so  new,  and  presenting  so  many 
obvious  practical  advantages  if  successful,  must  of  necessity  be  tried 
out  under  the  most  rigid  tests.  The  following  methods,  therefore, 
were  followed  in  the  two  years'  trials  at  Davis. 

1.  The  bunt  spores  were  grown  during  the  preceding  year  and 
consisted  only  of  spores  of  Tilletia  tritici  (Bjerk.)  Wint. 

2.  As  previous  experiments  had  been  rendered  inconclusive  by 
irregular  smut  infection,  a  graduated  scale  of  bunt  spore  dosage  was 
used.  Before  the  seed  was  treated  with  the  fungicide,  each  lot  was 
dosed  with  a  given  weight  of  bunt  spores  to  a  given  weight  of  wheat 
seed,  as  follows: 


Grades 

Bunt  Spores  in  Grams 

Wheat  Seed  in  Grams 

1 

1 

30 

2 

1 

250 

3 

1 

500 

4 

1 

750 

5 

1 

1000 

6 

1 

1500 

7 

1 

2000 

8 

1 

2500 

9 

1 

3000 

3.  Little  Club  wheat,  highly  susceptible  to  bunt  (pi.  3),  but  very 
resistant  to  lodging  and  shattering,  was  used  in  1921.  Because  of  its 
late  maturity  and  susceptibility  to  stem  rust,  it  was  replaced  in  1922 
by  White  Federation,  an  equally  bunt-susceptible  but  much  earlier 
variety  and  fairly  resistant  to  lodging  and  shattering. 


538  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

4.  The  quantity  of  chemical  dusts  applied  to  the  seed  was  grad- 
uated into  four  rates,  except  flowers  of  sulfur,  for  which  greater 
quantities  were  used. 

5.  The  plots  were  arranged  in  rows  separated  by  a  space  of  one 
foot.  The  seed  was  accurately  weighed  so  as  to  give  150  ±  2  kernels 
per  rod  row. 


Fig.  3. — No.  1,  bunted  Little  Club  and  bunt  gall  (natural  size).  No.  2,  normal 
Little  Club  bead  and  kernel.     Bunted  Club  wheat  shows  reduced  thickness  of  head. 

6.  Because  both  plants  as  well  as  heads  were  to  be  counted,  the 
seeds  were  dropped  by  hand  and  spaced  at  an  average  distance  of 
1%  inches.  As  approximately  50  per  cent  of  the  seed  fails  to  produce 
plants  in  the  soil  at  Davis,  the  harvested  plants  were  separated  on 
the  average  by  more  than  2y2  inches,  thus  making  possible  an  accurate 
separation  of  the  plants  at  harvest  time.  To  prevent  breaking  of 
plants,  the  soil  was  softened  by  irrigation  previous  to  pulling. 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT 


539 


INFLUENCE  OF  SPORE  LOAD  UPON  BUNT  ATTACK 

Field  observations  supported  by  counts  of  bunt  spores  on  seed 
wheat  indicate  that  the  number  of  spores  per  kernel  decidedly  in- 
fluence the  bunt  attack.  Seed  carrying  no  more  than  ten  spores  on 
each  kernel  has  not  been  observed  to  give  infection. 

The  seed  for  the  1921  crop  was  separated  into  nine  lots,  according 
to  the  quantity  of  bunt  spores  applied.  The  dosage  by  weight  ranged 
from  1  part  of  bunt  spores  to  30  parts  of  seed  wheat  (1-30)  to  1  to 
3000  parts  (1-3000).  This  last,  or  lightest  dosage,  yielded  several 
hundred  bunt  spores  per  kernel  (pis.  1  and  2). 

The  effect  of  variation  in  the  dosage  of  bunt  spores  on  seed  is 
shown  in  table  1. 


TABLE  1 

Summary  of  Bunt  Attack  According  to  the  Dosage  of  Spores. 
Experiments  Conducted  During  1921  and  1922  at  Davis 

Per  Cent  of  Bunt  by  Head  Count 


Spore 

Dosage 

to  Seed  by  Weight 

1-30 
Bunt 

1-250 
Bunt 

1-500 
Bunt 

1-750 
Bunt 

1-1000 
Bunt 

1-1500 
Bunt 

1-2000 
Bunt 

1-2500 
Bunt 

1-3000 
Bunt 

per 
cent 

per| 
cent 

perl 
cent 

per 
cent 

per 
cent 

per 
cent 

per 
cent 

per 
cent 

•    per 
cent 

Average  1921 

61.6 

37.3 

37.0 

28.7 

20.7 

■ 

16.3 

16.1 

10.6 

10.3 

Average  1922 

36.8 

41.4 

45.5 

39.6 

25.7 

31.9 

21.0 

These  results  show  that  the  bunt  attack  is  reduced  as  the  dosage 
is  decreased.  The  influence  of  spore  dosage  upon  the  effectiveness  of 
various  chemicals  is  very  marked  and  conforms  generally  to  the  scale 
of  bunt  reduction  shown  in  table  1.  The  scale  of  spore  dosage  is 
therefore  conducted  as  an  essential  part  of  every  set  of  experiments 
with  fungicidal  solutions  or  dusts.  Those  results  agree  closely  with 
those  secured  by  Heald,  at  Pullman,  Washington,15  whose  researches 
caused  him  to  believe  that  an  accurate  prediction  of  the  possible  bunt 
per  cent  in  a  crop  can  be  made  from  determination  of  the  number 
of  spores  on  the  seed  sown. 


540 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


CONTEOL  OF  BUNT  BY  SOLUTIONS  OF  STANDARD  FUNGICIDES 

Standard  solutions  previously  proven  effective  in  preventing 
infection  from  seed-borne  spores  were  used  as  checks  for  comparison 
wherever  fungicides  in  the  dust  or  powder  form  were  being  tested. 

TABLE  2 

Relative  Effectiveness   of  Standard   Fungicidal   Solutions   in   Preventing 

Bunt  Infection  Under  Varying  Dosages  of  Spores  in 

Experiments  Conducted  at  Davis 

Per  Cent  of  Bunt  by  Head  Count 


Treatment 


Check  (Untreated) 

Bluestone  (1-5)  3" 

Bluestone  (1-4)  3"  +  Lime 

d-8)5" 

Formaldehyde  (1-40)  10"  .... 


Spore  Dosage  to  Seed  by  Weight 


1-30 
Per 
Cent 
Bunt 


49.2 

2.5 

.7 
1.1 


1-250 
Per 

Cent 
Bunt 


1.2 


1-500 
Per 

Cent 
Bunt 


41.2 

.4 

.6 
.2 


1-750 
Per 
Cent 
Bunt 


34.1 


1-1000 
Per 
Cent 
Bunt 


23.2 
.3 

.1 

0.0 


1-1500 
Per 
Cent 
Bunt 


24.1 
0.0 

.1 
.1 


1-2000 
Per 
Cent 
Bunt 


18.5 
.1 

.1 
.1 


1-2500 
Per 
Cent 
Bunt 


10.6 
0.0 

.1 
.1 


1-3000 
Per 
Cent 
Bunt 


10.3 
0.0 

0.0 

.2 


All  three  of  the  standard  fungicidal  solutions  are  shown  to  be 
practically  completely  effective  when  properly  applied  even  for  the 
very  heaviest  dosage  of  bunt  spores  used  in  these  experiments.  It 
remains,  therefore,  to  compare  the  effectiveness  of  fungicidal  dusts 
and  powders  with  the  fungicidal  solutions. 


EFFECT  OF  FLOWERS  OF  SULFUR  ON  THE  CONTROL  OF  BUNT 

Farmers  from  time  to  time  have  reported  successful  control  of 
bunt  by  means  of  flowers  of  sulfur.  To  test  the  efficacy  of  this  dust, 
exhaustive  experiments  were  conducted  at  Davis  in  1919,  1920  and 
1921.  The  experiments  in  1919  indicated  that  sulfur  was  not  fully 
effective  against  infection  when  the  seed  was  blackened  with  bunt. 
The  experiments  in  1920  showed  that  sulfur  and  seed  wheat  mixed 
and  drilled  at  the  rate  of  25  pounds  of  flowers  of  sulfur  to  100  pounds 
of  seed  reduced  bunt  to  one-tenth  (61.8  per  cent  to  6.3  per  cent), 
but  in  no  case  eliminated  it.  Sulfur  produced  no  effect  in  preventing 
infection  from  spores  already  in  the  soil. 

In  order  finally  to  determine  the  limitations  of  flowers  of  sulfur 
as  a  bunt  fungicide,  135  tests  with  this  dust  were  made  at  Davis  in 
1921.  The  usual  rod-row  method  was  employed.    The  dosage  of  bunt 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT  541 

spores  applied  to  the  seed  was  arranged  in  nine  lots,  varying  from 
1-30  to  1-3000  by  weight.  The  results  of  these  duplicate  experiments 
are  summarized  in  table  3. 


TABLE  3 

Effectiveness  of  Flowers  of  Sulfur  in  Preventing  Bunt  Infection  Under 

Varying  Dosages  of  Spores  in  Experiments  Conducted 

During  1921  at  Davis 

Per  Cent  of  Bunt  by  Head  Count 


Treatment 


Check  (Untreated) 

Dipped  Bluestone  (1-5)  3"  .. 
Dipped  bluestone  (1-4)  8"; 

limed  (1-8)  5"...., 

Dipped  formaldehjyde 

(1-40)  10" 

Sulfured  25  lbs.  per  100  lbs. 

seed 

Sulfured  15  lbs.  per  100  lbs. 

seed 

Sulfured  5  lbs.  per  100  lbs. 

seed 

Sulfured  2  lbs.  per  100  lbs. 

seed 

Sulfured  1  lb.  per  100  lbs. 

seed 

Sulfured  Y2  lb.  per  100  lbs. 

seed 

Sulfured  \i  lb.  per  100  lbs. 

seed 


Spore  Dosage  to  Seed  by  Weight 


1-30 
Per 
Cent 
Bunt 


61.5 

.9 

.2 
2.4 

32.6 
43.5 
37.0 
49.9 
48.6 
56.8 
65.4 


1-250 
Per 
Cent 
Bunt 


47.3 
1.5 

.1 

3.0 
7.2 
5.6 
18.1 
28.0 
44.0 
35.4 
51.9 


1-500 
Per 
Cent 
Bunt 


51.3 

.6 

0.0 

.2 

5.2 

9.3 

19.0 

20.3 

28.0 

32.1 

34.6 


1-750 
Per 
Cent 
Bunt 


35.4 
.3 

0.0 

0.0 

6.9 

6.2 

10.5 

14.2 

21.6 

22.6 

18.4 


1-1000 
Per 

Cent 
Bunt 


31.6 
.3 

.4 

0.0 

4.0 

4.2 

9.5 

14.4 

17.5 

17.0 

20.4 


1-1500 
Per 
Cent 
Bunt 


26.5 
0.0 

0.0 

0.0 

2.5 

4.8 

5.2 

7.4 

16.4 

11.7 

16.5 


1-2000 
Per 
Cent 
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21.6 
0.0 

0.0 

0.0 

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2.2 
4.0 
7.1 

6.8 

7.2 
7.9 


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0.0 

0.0 

.1 

.5 

3.8 

.2 

4.2 

7.0 

5.2 


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10.9 
0.0 

0.0 

0.0 

.1 

1.0 

.6 
2.6 
2.6 
4.4 

8.7 


The  evidence  of  these  experiments  with  sulfur  indicate:  (1)  that 
flowers  of  sulfur  sown  with  seed  at  rates  varying  from  %  to  25  pounds 
of  sulfur  per  100  pounds  of  seed,  reduces  seed-borne  infection  but 
does  not  wholly  prevent  it;  (2)  as  the  quantity  of  sulfur  is  increased 
from  14  pound  to  25  pounds  per  100  pounds  of  seed,  the  bunt  attack 
is  correspondingly  reduced,  but  even  the  25  pound  rate  does  not 
entirely  prevent  infection;  and  (3)  because  of  these  limitations 
flowers  of  sulfur  cannot  be  recommended  as  a  practical  remedy  for 
bunt  control. 


542 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


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Bulletin  364]        FUNGICIDAL  DUSTS  FOR  THE  CONTROL  OF  BUNT  543 

CONTROL    OF   BUNT    BY   COPPER   SULFATE   POWDER 

Bluestone  and  bluestone-lime  solutions  for  seed  treatment  are 
preferred  on  the  Pacific  Coast  to  formaldehyde  because  seed  injury 
is  generally  less,  and,  in  addition,  bluestone  has  a  residual  repressive 
effect  against  infection  from  bunt-infested  soils.  It  is  natural,  there- 
fore, that  bluestone  and  bluestone-lime  powder  should  be  tested  when 
dry  treatments  were  considered.22 

The  results  of  two  years'  experiments  with  bluestone  powder  are 
reported  in  table  4. 

Bluestone  was  prepared  in  various  ways  to  test  its  effectiveness. 
First,  powdered  bluestone  was  shaken  up  with  wheat  at  the  rates  of 
one,  two,  three,  and  four  ounces  per  bushel  of  seed.  As  powdered 
bluestone  is  simply  a  mass  of  finely-divided  crystals,  the  term  powder 
is  employed  to  differentiate  it  from  copper  carbonate  dust,  which  is 
not  crystalline,  but  amorphous. 

As  bluestone  powder  appeared  to  be  caustic  to  seed  germs,22  lime 
dust  was  added  in  sufficient  quantities  to  react  with  the  bluestone — 
usually  two  parts  of  bluestone  to  one  part  of  lime,  as  is  the  case  with 
the  liquid  bluestone-lime  method  of  seed  treatment. 

The  increase  in  the  amount  of  the  bluestone  powder  from  one  to 
two  ounces  per  bushel  of  seed  in  every  case  markedly  increased  its 
efficiency,  but  further  increase  to  three  and  four  ounces  per  bushel 
reduced  the  bunt  attack  little  or  not  at  all.  It  is  evident,  therefore, 
that  two  or  three  ounces  per  bushel  are  ample  for  the  most  effective 
control  by  this  fungicidal  powder. 

Because  seed  injury  from  bluestone  dust  was  anticipated,  lime 
dust  (CaC03)  was  added  in  sufficient  quantities  to  react  chemically 
with  the  bluestone.  The  results  show  in  every  case  that  the  addition 
of  lime  decreased  the  effectiveness  of  the  bluestone  by  increasing  the 
bunt  attack  from  two  to  four  times.  As  sound  seed  does  not  show 
any  injurious  effect  from  the  bluestone  powder  for  any  of  the  doses 
from  one  to  four  ounces  per  bushel,  there  appears  to  be  no  necessity 
for  adding  the  lime. 

One  disadvantage  of  copper  sulfate  is  its  tendency  to  consolidate 
into  masses,  losing  its  powder  form.  This  condition  was  thought 
to  be  due  to  the  five  molecules  of  water  contained  in  bluestone 
(CuS04.5H20).  Bluestone  was  heated  to  103°  C.  and  206°  C.  respec- 
tively. Of  the  water  of  crystallization,  only  one  molecule  remained 
(CuS04.H,0)  at  103°  C,  and  water-free  anhydrous  copper  sulfate 
(CuSOJ  was  secured  at  206°  C.  After  months  of  exposure  to  air, 
these  anhydrous  copper  sulfate  powders  still  remained  powdered  and 
apparently  unaltered. 


544 


UNIVERSITY    OF   CALIFORNIA — EXPERIMENT    STATION 


TABLE  5 

Use  of  Anhydrous  Copper  Sulfate  in  Preventing  Bunt  Infection  Under  a 
Dosage  of  Spores  of  1 : 750 

Experiments  Conducted  During  1922  at  Davis 

Per  Cent  of  Bunt  by  Head  Count 


Treatment 


Germination 
Per  Cent 

Lab. 

Field 

99.8 

68.0 

49.3 

35.0 

92.0 

36.6 

99.6 

48.2 

98.0 

51.0 

100.0 

54.3 

99.0 

55.0 

98.0 

48.0 

100.0 

53.3 

98.0 

54.6 

Per  Cent 
Bunt 


Check  (untreated) 

Dipped  bluestone  (1-5)  3" 

Dipped  bluestone  (1-4)  3";  limed  (1-8)  5" 

Dipped  formaldehyde  (1-40)  10" 

Dusted  bluestone* — -2  oz 

Dusted  bluestone* — 4  oz 

Dusted  bluestone  dehydrated f  at  103°  C. — 2  oz. 
Dusted  bluestone  dehydrated f  at  103°  C. — 4  oz. 
Dusted  bluestone  dehydrated f^at  206°  C .—  2  oz. 
Dusted  bluestone'dehydratedfat  206°  C. — 4  oz. 


28.6 
0.0 
0.0 
0.0 
6.6 
1.2 
.1 
0.0 
0.0 
0.0 


*  Bluestone  analyzed  98.27  per  cent  pure. 

t  Bluestone   (CuS04.5H20)    dehydrated  at   103°  C.  loses  4  molecules  of  water, 


becoming   CuS04.H20. 
(CuS04)  is  secured. 


When   dehydrated   at    206°  C,   the  pure    anhydrous    form 


The  tests  in  table  5,  made  in  duplicate,  gave  the  following  results 
for  a  bunt  dosage  of  1  to  750 : 

1.  The  checks  with  the  standard  solutions  of  bluestone,  bluestone- 
lime,  and  formaldehyde  were  practically  completely  effective  (over 
99  per  cent). 

2.  Other  experiments  not  here  reported  showed  that  the  addition 
of  salt  (NaCl)  or  lime  (CaC03)  to  the  bluestone  powders  did  not 
materially  help  its  efficiency,  but,  on  the  contrary,  lime  sometimes 
reduced  bunt  control.     Germination  was  not  affected. 

3.  Bluestone,  dehydrated  at  temperatures  of  103°  C.  and  206°  C, 
caused  no  material  change  in  the  effectiveness  of  the  bluestone  powder. 

4.  The  results  obtained  with  anhydrous  copper  sulfate  indicate 
no  improvement  in  the  control  of  bunt  or  the  prevention  of  seed 
injury.  However,  the  anhydrous  form  remains  in  a  pulverized  con- 
dition much  more  certainly  than  powdered  bluestone. 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT  545 


COPPER  SULFATE  DUST  AS  A  SUBSTITUTE  FOE  COPPER  CARBONATE 

As  copper  sulfate,  or  bluestone,  is  the  basis  for  copper  carbonate 
manufacture,  there  appears  to  be  no  reason  why  sufficient  quantities 
of  copper  carbonate  should  not  be  manufactured. 

Malachite,  a  copper  carbonate  mineral  occurring  in  the  United 
States,  was  investigated,  but  it  was  found  to  be  available  in  very 
limited  quantities,  and  rather  impure.  Experiments  demonstrated 
that  malachite  as  a  bunt  preventive  was  greatly  inferior  to  well- 
prepared  copper  carbonate  dust. 

If,  however,  copper  carbonate  dust  is  not  available  in  sufficient 
quantities,  powdered  bluestone  may  be  used  as  a  good  substitute. 
Experiments  conducted  at  Davis  and  in  cooperation  with  farmers 
were  successful,  but  the  results  were  not  as  satisfactory  as  those  in 
which  copper  carbonate  dust  was  used.  The  greatest  difficulty  offered 
by  bluestone  lies  in  the  fact  that  it  is  not  easily  reduced  to  a  powder 
and  in  the  further  fact  that  it  is  difficult  to  maintain  it  in  a  loose 
powdered  form  sufficiently  fine  to  adhere  to  seed. 


MISCELLANEOUS  CHEMICAL  DUSTS 

In  addition  to  copper  sulfate  powder  and  copper  carbonate  dust, 
many  other  chemical  powders  and  dusts  were  tested  in  an  attempt  to 
secure  a  common  and  relatively  cheap  fungicide.  The  list  included 
malachite,  paris  green,  barium  carbonate,  lead  carbonate,  ferrous 
sulfate,  manganese  dioxide,  calcium  carbonate,  potassium  sulfate, 
ammonium  sulfate,  sodium  nitrate,  superphosphate,  sodium  carbonate, 
sodium  chloride,  magnesium  sulfate,  and  various  combinations  of  lime 
and  fungicides  and  of  fertilizers.  Some  of  them  possess  decided  fungi- 
cidal properties,  but  all  were  far  inferior  to  copper  carbonate  and 
copper  sulfate  in  control  of  bunt.  Seed  injury  occurred  with  paris 
green  and  superphosphate,  but  the  addition  of  lime  dust  reduced  or 
removed  the  injurious  effects. 


EFFECT  OF  COPPER  CARBONATE  DUST  ON  THE  CONTROL  OF  BUNT 

The  accuracy  of  scientific  experiments  increases  with  the  number 
of  replications.  The  experiments  with  copper  carbonate  dust  con- 
ducted for  three  years  were  repeated  in  duplicate  in  many  series. 
During  this  period  approximately  1,600,000  plants  and  8,100,000 
heads  were  individually  examined,  counted,  and  recorded. 


546 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


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BULLETIN    364]         FUNGICIDAL   DUSTS   FOR   THE    CONTROL   OF   BUNT  547 

The  results  obtained  are  reported  (1)  in  table  6,  covering  experi- 
ments with  copper  carbonate  dust  upon  various  dosages  of  bunt 
spores;  (2)  in  table  7,  treating  the  subject  of  dilution  of  copper 
carbonate;  and  (3)  table  8,  relating  to  the  effect  of  the  chemical 
purity  and  physical  fineness  of  copper  carbonate  upon  bunt  control. 

In  order  to  make  these  experiments  as  comprehensive  as  possible, 
and  thus  anticipate  many  questions  likely  to  arise  concerning  the 
dust  fungicides,  nine  rates  of  dosages  of  spores  and  four  rates  of 
chemical  treatment  were  used.  The  copper  carbonate  treatments  were 
checked  against  untreated  seed  and  seed  treated  with  the  standard 
solutions,  and  compared  with  bluestone  powder.  The  experiments 
with  bluestone  powder  were  carried  on  in  connection  with  the  copper 
carbonate  dust  because  the  former  is  always  available  and  much 
cheaper  than  copper  carbonate  dust. 

In  order  to  render  the  data  on  copper  carbonate  more  readily 
comparable,  the  statistical  results  of  each  year  (1921  and  1922)  have 
been  summarized  and  placed  adjacent. 

The  relative  results  of  the  two  seasons  do  not  vary  in  general  and 
in  no  case  is  there  a  reversal  in  comparing  each  set  of  experiments. 
The  results  of  the  two  years'  tests  are,  therefore,  discussed  together. 

With  the  decrease  of  the  spore  dosage,  the  per  cent  of  bunt 
invariably  decreased  and  directly  affected  the  tests  with  the  fungicidal 
dusts  which  followed. 

The  standard  fungicidal  solutions,  bluestone,  bluestone-lime,  and 
formaldehyde,  were  practically  fully  effective,  except  for  the  heaviest 
dosage  of  blunt  spores  (1-30).  So  small  was  the  difference  between 
these  three  solutions  that  any  one  of  them  may  be  recommended  so 
far  as  concerns  the  control  of  bunt  from  seed-borne  spores.  For 
reasons  already  advanced,  the  bluestone-lime  method  is  preferred  on 
the  Pacific  Coast  when  it  comes  to  a  choice  of  solutions. 

When  compared  with  the  fungicidal  solutions,  copper  carbonate 
is  seen  to  be  less  effective  for  the  heavier  dosages  (1-30  and  1-250), 
but  is  very  effective  for  dosages  of  1-750  and  less. 

Copper  carbonate  dust  applied  at  four  rates  (1,  2,  3,  and  4  ounces 
per  bushel)  when  compared  with  the  standard  solutions,  was  found 
to  be  less  effective  up  to  a  bunt  spore  load  of  1-750,  where  it  approxi- 
mately completely  controlled  infection.  At  this  point  the  seed  is 
visibly  darkened  and  is  much  smuttier  than  is  advisable  to  sow  under 
any  circumstances  (pis.  1  and  2).  For  the  spore  loads  of  1-750 
and  less  there  was  no  gain  in  bunt  control  by  increasing  the  dose 
of  copper  carbonate  beyond  two  ounces  per  bushel.  However,  two 
ounces  usually  was  found  to  be  more  effective  than  smaller  quantities. 


548  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Copper  carbonate  in  every  instance  was  found  to  be  more  efficient 
than  bluestone  powder  with  or  without  lime.  For  dosages  of  1-750 
or  less,  copper  carbonate  was  as  efficient  as  the  formaldehyde  and 
bluestone  treatments. 

EFFECT  OF  THE  DILUTION  OF  COPPER  CARBONATE  ON  BUNT 

CONTROL 

Copper  carbonate  dust  when  properly  made  contains  more  than 
50  per  cent  of  copper  in  the  form  of  a  compound  of  carbonate  and 
hydrate  of  copper  (CuC03.Cu(OH)2)  as  basic  copper  carbonate.  As 
this  chemical  is  usually  more  than  twice  as  rich  in  copper  as  blue- 
stone  (CuS04.5H20),  containing  25.4  per  cent  copper,  it  has  been 
advocated  that  a  more  dilute  basic  copper  carbonate  could  be  used. 
Copper  carbonate  dust  of  standard  strength  was  therefore  mixed  with 
gypsum  (CaS04.2H20)  or  with  lime  (CaC03)  in  a  series  of  graded 
mixtures.     The  results  on  bunt  control  are  reported  in  table  7. 

The  reduction  of  the  spore  load  on  the  seed  returned  a  corre- 
sponding reduction  of  bunt  attack  for  untreated  as  well  as  for  all 
treated  seed. 

Gypsum  added  to  copper  carbonate  decreased  its  efficiency  as  a 
bunt  preventive,  in  proportion  to  the  amount  added.  Increased 
amounts  of  fungicidal  dust  from  two  to  four  ounces  per  bushel  gave 
a  corresponding  decrease  in  the  percentage  of  bunt,  and  with  the 
decrease  of  the  gypsum  from  3  to  1  to  pure  copper  carbonate,  there 
was  a  corresponding  decrease  in  the  percentage  of  bunt. 

The  dilution  of  copper  carbonate  with  lime  dust  gave  almost 
identically  the  same  results  as  dilution  with  gypsum,  except  that  the 
control  of  bunt  was  somewhat  less. 

These  experiments  indicate  that  no  beneficial  results  may  be 
expected  from  diluting  copper  carbonate  with  non-fungicidal  powders 
or  dusts.  However,  it  appears  that  copper  carbonate  may  be  diluted 
at  the  rate  of  25  per  cent  without  seriously  reducing  its  effectiveness. 
If  the  dilution  is  increased  to  50  per  cent,  the  rate  of  treatment,  to 
be  effective,  must  be  increased  to  four  ounces  per  bushel,  which  means 
that  copper  carbonate  is  actually  added  at  the  rate  of  two  ounces  per 
bushel.  Four  ounces  of  dust  is  considerably  more  than  will  adhere 
to  the  seed.  In  these  experiments  the  excess  dust  was  sown  with  the 
seed.  However,  dusting  machines  are  devised  to  take  out  all  the 
dust  except  the  quantity  which  adheres  to  the  seed.  If  an  excess 
of  dust  were  left  with  the  seed  it  would  be  blown  away  when  broad- 
cast seeders  are  used.  A  dilution  of  this  dust  would  directly  reduce 
the  active  fungicide.  A  concentrated,  highly  efficient  dust  fungicide 
is  therefore  deemed  necessary. 


Bulletin  364 


FUNGICIDAL   DUSTS   FOR   THE    CONTROL    OF    BUNT 


549 


TABLE  7 

The  Effect  of  Diluting  Copper  Carbonate  on  its  Use  in  Preventing  Bunt 

Infection  Under  Varying  Dosages  of  Bunt  Spores 

Experiments  Conducted  During  1922  at  Davis 

Per  Cent  of  Bunt  by  Head  Count 


Fungicide  and  Treatment 


Check  (Untreated) 

Solutions: 

Bluestone  (1-5)  3" 

Bluestone  (1-4)  3";  limed  (1-8)  5" 

Formaldehyde  (1-40)  10" 

Dusts: 

1  part   CuC03  to  3  parts  CaS04 — 2  oz.  to  bu. 

1  part  CuC03  to  1  part   CaS04 — 2  oz.  to  bu. 

3  parts  C11CO3  to  1  part   CaS04 — 2  oz.  to  bu. 

1  part   CuC03  to  0  part   CaS04 — 2  oz.  to  bu. 

1  part  CuC03  to  3  parts  CaS04 — 4  oz.  to  bu. 
1  part  CuC03  to  1  part  CaS04 — 4  oz.  to  bu. 
3  parts  CuC03  to  1  part  CaS04— 4  oz.  to  bu. 
1  part   CuC03  to  0  part  CaS04 — 4  oz.  to  bu. 

1  part  CuC03  to  3  parts  CaC03 — 2  oz.  to  bu. 
1  part  CuC03  to  1  part  CaC03 — 2  oz.  to  bu. 
3  parts  CuC03  to  1  part  CaC03 — 2  oz.  to  bu. 
lpart  CuC03 to  Opart  CaC03— 2  oz.  to  bu. 

1  part  CuC03  to  3  parts  CaC03 — 4  oz.  to  bu. 
1  part  CuC03  to  1  part  CaC03 — 4  oz.  to  bu. 
3  parts  CuC03  to  1  part  CaC03 — 4  oz.  to  bu. 
1  part  CuCO/to  0  part  CaC03 — 4  oz/to  bu. 


Germination 
per  Cent 


Lab. 


91.3 

22.0 
60.3 
93.3 

91.0 
90.0 
94.0 
95.0 

98.0 
94.0 
95.0 
97.0 

95.0 
95.0 
95.0 
94.0 

94.0 
95.0 
91.0 
90.0 


Field 


48.6 

25.2 
35.5 
37.1 

52.6 
52.0 
53.6 
54.3 

51.6 
52.3 
50.6 
57.3 

58.6 
56.3 
49.6 
50.6 

53.0 
49.6 
46.6 
56.3 


Spore  Dosage  to  Seed 
by  Weight 


1-250 
Per 
Cent 
Bunt 


40.6 
1.1 

2.7 
0.0 

29.4 

23.4 

11.8 

4.9 

17.4 
2.3 
1.6 

.7 

20.7 

20.4 

5.1 

2.8 

17.5 
10.0 

.7 
1.6 


1-750 
Per 
Cent 
Bunt 


47.4 

.3 
1.7 

0.0 

12.6 

5.2 

.2 

1.1 

3.9 

.2 

0.0 


18.3 
7.1 
1.1 
1.0 

5.6 
1.7 

.7 
.5 


1-1500 
Per 
Cent 
Bunt 


33.4 

1.6 

.2 

0.0 

5.9 

1.1 

.5 

.2 

1.1 
0.0 
0.0 

0.0 

9.7 

2.0 

.1 

.1 

3.6 
.9 
.1 

0.0 


COMPAEATIVE    EFFECTIVENESS    OF    SOME    COMMERCIAL    SAMPLES 
OF  COPPER  CARBONATE 

Copper  carbonate  dust  from  many  sources  has  been  sold  on  the 
Pacific  Coast  to  be  used  for  control  of  bunt.  Due  probably  to  differ- 
ences in  manufacture,  no  two  commercial  brands  are  identical  in 
chemical  and  physical  composition.  In  order  to  ascertain  the  effect 
of  these  differences  in  copper  carbonate  dust,  a  number  of  commercial 
brands  were  tested  to  determine  their  efficiency  in  control  of  bunt. 
The  results  are  reported  in  table  8. 


550 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Copper  carbonate  No.  1  (table  8)  appeared  to  be  physically  and 
chemically  satisfactory  and  gave  satisfactory  bunt  control  for  spore 
dosages  of  1-750  and  less.  Number  2  gave  results  very  similar  to 
No.  1,  except  that  it  was  more  efficient  for  the  1-750  spore  dosage. 
Sample  No.  3  was  not  satisfactory,  giving  poor  bunt  control  for  all 
tests.     This  sample  did  not  possess  the  light  green  fluffy  appearance 


TABLE  8 

The  Difference  in  Effectiveness  of  Some  Commercial  Samples  of  Copper 

Carbonate  in   Preventing  Bunt  Infection   Under 

Varying  Dosages  of  Spores 

Experiments  Conducted  During  1922  at  Davis 

Per  Cent  of  Bunt  by  Head  Count 


Fungicide  and  Treatment 


Check  (Untreated) 

Solutions: 

Bluestone  (1-5)  3" 

Bluestone  (1-4)  3";  limed  (1-8)  5' 

Formaldehyde  (1-40)  10" 

Chlorophol  II,  2-3  gr.  litre 

Dnsts: 

CuC03— No.  1—2  oz.  to  bu 

CuCOs— No.  1—4  oz.  to  bu 

CuC03— No.  2—2  oz.  to  bu 

CuC03— No.  2—4  oz.  per  bu 

CuC03— No.  3—2  oz.  per  bu 

CuC03— No.  3—4  oz.  per  bu 

CuC03— No.  4—2  oz.  per  bu 

CuC03 — No.  4 — 4  oz.  per  bu 

Chlorophol — No.  2 — 2  oz.  per  bu 

Chlorophol — No.  2 — 4  oz.  per  bu 


Germination 
per  Cent 


Lab. 


93.5 

24.5 
56.0 
81.0 
93.5 

91.0 
93.0 
94.0 
94.0 
93.0 
95.0 
91.0 
93.0 
93.0 
91.0 


Field 


54.13 

29.8 
44.0 
35.6 
60.3 

58.9 
55.2 
57.3 
59.5 
55.1 
56.6 
59.8 
58.1 
60.4 
59.1 


Spore  Dosage  to  Seed 
by  Weight 


1-250 
Per 
Cent 
Bunt 


52.8 


1.3 
.2 
.1 

5.5 

4.3 

8.9 

3.7 

23.2 

21.1 

16.1 

9.9 

19.4 

3.3 


1-750 
Per 
Cent 
Bunt 


37.1 

0.0 
.2 
.1 

0.0 


.4 
1.6 

.1 
0.0 
9.9 
4.4 
5.1 

.4 
2.4 
1.0 


1-1500 
Per 

Cent 
Bant 


20.4 

.4 

.3 

0.0 

0.0 

.3 

0.0 

1.1 

0.0 
2.4 
3.6 
2.5 
.2 
.4 
1.6 


of  the  satisfactory  samples,  but  was  denser  and  coarser  and  of  a 
darker  color.  Sample  No.  4  gave  satisfactory  control  when  applied 
at  the  rate  of  4  ounces  per  bushel,  but  was  unsatisfactory  at  the  rate 
of  2  ounces.  It  is  a  commercial  compound  with  a  copper  carbonate 
base  and  contains  about  half  as  much  copper  as  pure  copper  car- 
bonate. Since  it  was  necessary  to  use  4  ounces  per  bushel,  approxi- 
mately the  same  quantity  of  copper  was  required  as  if  2  ounces  of 
copper  carbonate  had  been  used. 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT  551 

Chlorophol  (a  patented  chloro-phenol-mercuric  compound),27'28 
gave  excellent  control  as  a  liquid.  The  results  indicate  that  organic 
mercuric  compounds  offer  possibilities  as  dust  fungicides. 


EFFECT   OF  FUNGICIDAL  DUSTS   UPON  SEED   GERMINATION 

Fungicidal  solutions  employed  to  control  infection  from  seed- 
borne  bunt  spores  have  been  shown  to  cause  severe  injury  to  seed 
germination,6, 16> 21  and  great  reduction  in  germination.  When  such 
seed  is  sown  in  the  field,  poor  stands  result  unless  overcome  by  a 
very  heavy  increase  in  the  rate  of  seeding.  Farmers  have  reported 
sowing  from  120  to  200  pounds  of  wheat  per  acre  in  an  effort  to 
overcome  seed  losses,  a  very  considerable  portion  being  due  to  seed 
treatment.  As  will  be  shown  later,  the  soil  itself  takes  a  heavy  toll 
of  seed. 

When  seed  is  dusted  with  copper  carbonate  it  may  be  left  in- 
definitely without  fear  of  seed  injury  so  far  as  the  fungicide  is 
concerned.14  It  even  appears  to  have  a  somewhat  repellent  effect 
upon  grain  weevils.  As  copper  carbonate  dust  does  not  attract 
moisture  from  the  air,  no  reaction  occurs  until  it  comes  in  contact 
with  the  soil  moisture.  When  there  is  sufficient  soil  moisture  to  start 
germination,  moisture  conditions  are  satisfactory  for  causing  the 
copper  carbonate  to  go  into  solution  and  become  active. 

All  treated  seed  sown  in  the  plots  was  tested  in  the  seed-testing 
laboratory  of  the  United  States  Department  of  Agriculture.*  At 
harvest  time  all  plants  were  pulled  and  counted,  and  were  then 
classified  as  bunted  or  clean.  In  this  manner,  a  practical  check  on 
the  survival  of  the  seed  sown  in  the  soil  was  recorded.  The  germina- 
tion of  seed  under  laboratory  and  field  conditions  are  given  in  table  9. 

It  is  evident  at  once  that  the  chemical  solutions  cause  a  great 
deal  of  injury  to  germination.  On  an  average,  only  31.4  per  cent 
of  the  bluestoned  seed  survives  in  the  soil,  and  but  slightly  more 
(39.6  per  cent)  under  germination  in  the  laboratory.  The  bluestone- 
lime  dips  show  very  favorable  germination  in  the  laboratory  (73.6 
per  cent),  but  little  more  than  half  (53.8  per  cent)  as  much  when 
germinated  in  the  soil.  The  lime  bath  following  the  bluestone  solu- 
tion saves  26  per  cent  of  the  seed  when  compared  with  the  bluestone 
alone.  The  formaldehyde  under  the  favorable  soil  and  moisture  con- 
ditions at  Davis  gave  as  high  germination  in  the  soil  as  bluestone-lime. 

The  chemical  dusts,  as  a  whole,  cause  practically  no  injury  when 
compared  with   the   untreated   checks.      Some   depression   appeared 


552 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


when  common  salt  (NaCl)  was  added  to  the  bhiestone  powder.  To 
offset  the  depression  caused  by  the  salt,  lime  was  added,  with  the 
result  that  the  germination  in  soil  was  considerably  superior  to  the 
untreated  check  plots.  The  addition  of  the  lime,  however,  reduced 
the  control  of  bunt.  Copper  carbonate  dust  in  a  large  number  of 
experiments  gave  somewhat  better  germination  in  the  soil  than  the 
untreated  seed. 

TABLE  9 

Influence  of  Seed  Treatment  on  the  Per  Cent  of  Germination   of  Seed 

Tested  in  the  Laboratory  at  Berkeley  and  Seed  Planted  in 

the  Field  at  Davis  During  1921  and  1922 


Fungicide  and  Treatment 


No.  of 
tests 


Germination 
Per  Cent 


*Lab. 


Field 


Check  (Untreated) 

Solutions: 

Bluestone  (1-5)3" 

Bluestone  (1-4)  3";  limed  (1-8)  5" 

Formaldehyde  (1-40)  10" 

Dusts: 

Copper  carbonate — 4  oz.  to  bu 

Bluestone — 4  oz.  to  bu 

Bluestone +lime  (2-1) — 6  oz.  to  bu 

Bluestone  dehydrated  at  103°  C — 4  oz.  to  bu.f 

Bluestone  dehydrated  at  206°  C — 4  oz.  to  bu.... 

1  part  CuC03  to  3  parts  gypsum — 4  oz.  to  bu... 

1  part  CuC03  to  1  part  gypsum — 4  oz.  to  bu.  .. 

3  parts  CuC03  to  1  part  gypsum — 4  oz.  to  bu.  . 

Sulfur:  25  lbs.  per  100  lbs.  seed 


112 

112 
112 
112 

32 

32 

32 

2 

2 
6 
6 
6 

18 


95.1 

38.1 
73.6 
93.6 

96.2 
95.4 
97.2 
98.0 
98.0 
98.0 
94.0 
95.0 
99.0 


53.8 

31.4 
39.6 
41.5 

54.2 
53.0 
53.3 
48.0 
54.6 
51.6 
52.3 
50.6 
53.2 


*  We  are  indebted  to  Miss  Etta  Gilbert  and  Miss  Grace  Cole  of  the  California 
Branch  of  the  Seed  Laboratory  for  germination  tests. 

t  Bluestone  (CuS04.5H20)  dehydrated  at  103°  C.  loses  4  molecules  of  water, 
becoming  CuS04.H20.  When  dehydrated  at  206°  C.  the  pure  anhydrous  form, 
CuS04,  is  secured. 


The  effect  of  the  soil  (Yolo  silt  loam)  at  Davis  on  seed  germination 
was  to  reduce  the  natural  air  germination  of  seed  wheat  from  95.1 
per  cent  to  53.8  per  cent.  Soils  of  a  sandier  texture  would,  of  course, 
give  better  germination  than  those  at  Davis,  but,  on  the  other  hand, 
harsher,  heavier,  poorly  drained  soils  would  give  poorer  germination 
and  stands  of  grain.  Undoubtedly  the  rate  of  seeding  and  consequent 
stand  of  grain  is  greatly  influenced  by  the  effect  of  soil  texture  on 
treated  as  well  as  untreated  seed. 


PLATE  1 

White  Federation  wheat.  Dorsal  side,  X  30  diameters.  Bunted  at  the  rate  of 
1  part  bunt  spores  to  3000  parts  of  seed.  Approximately  1600  bunt  spores  per 
kernel.15  As  these  are  so  few  they  are  not  visible  to  the  naked  eye  and  the  seed 
passes  as  bunt  free. 


PLATE  2 

X  30 


White  Federation  wheat.  Ventral  side,  X  30  diameters.  Bunted  at  the  rate 
of  1  part  of  bunt  spores  to  3000  parts  of  seed.  Approximately  1600  bunt  spores 
per  kernel.15  As  these  are  so  few  they  are  not  visible  to  the  naked  eye  and  the 
seed  pass  as  bunt  free. 


PLATE  3 


Little  Club.  Bunt  free.  Dorsal  and  ventral  sides.  X  30  diameters.  The 
surface  of  seed  wheat  appears  smooth  to  the  naked  eye,  but  the  surface  is  here 
seen  to  be  quite  rough  and  capable  of  holding  spores  and  copper  carbonate  dust 
readily. 


BULLETIN    364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT 


553 


STIMULATION  OF  WHEAT  SEEDLINGS  BY  COPPEE  CAEBONATE  DUST 

Although  the  experiments  conducted  during  192022-  23  were  very 
limited  in  scope,  they  clearly  indicated  that  no  injury  to  germination 
resulted  from  treating  seed  wheat  with  copper  carbonate.  Germina- 
tion tests  conducted  in  the  laboratory  at  Berkeley  and  in  the  field 
at  Davis  in  connection  with  a  large  number  of  experiments  during 


Fig.  4. — Stimulation  of  wheat  seedlings  by  copper  carbonate  dust. 

a.  Effect  of  fungicidal  dusts  on  wheat  seedlings.  Left  to  right:  No.  1,  un- 
treated seed;  No.  2,  bluestone  dust  applied  at  the  rate  of  4  ounces  per  bushel; 
No.  3,  bluestone-lime  dust  mixed  (2  to  1)  and  applied  6  ounces  per  bushel;  No.  4, 
copper  carbonate  dust,  4  ounces  per  bushel. 

b.  Effect  of  fungicidal  solutions  upon  wheat  seedlings:  left  to  right:  No.  5, 
untreated  seed;  No.  6,  bluestone  solution  (1  lb.  to  5  gals.),  soaked  3  minutes; 
No.  7,  bluestone  dip  (1  lb.  to  4  gals.),  soaked  5  minutes,  followed  by  lime  bath 
(1  lb.  to  8  gals.),  applied  5  minutes;  No.  8,  formaldehyde  solution  (1  pt.  to  40 
gals.),  submerged  10  minutes. 

1921  and  1922,  show  that  seed  treated  with  copper  carbonate  dust 
is  equal  to  untreated  seed  and  is  superior  to  seed  treated  by  the 
standard  solutions.  Seed  treated  with  copper  carbonate  sprouted 
a  few  days  earlier  and  grew  more  vigorously  throughout  the  season 
than  the  others. 

Preliminary  greenhouse  experiments  on  wheat  seedlings  likewise 
indicate  a  decided  stimulation  following  the  use  of  copper  carbonate. 


554  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

Numerous  demonstrations  on  the  use  of  copper  carbonate  treat- 
ments have  been  conducted  throughout  the  state  under  the  supervision 
of  the  farm  advisors.  All  agree  that  no  seed  injury  is  evident  where 
copper  carbonate  is  used.  Many  report  that  seedlings  from  copper- 
carbonate  treated  seed  emerge  earlier  and  grow  more  vigorously  than 
seedlings  from  untreated  seed  or  from  seed  treated  with  the  usual 
solutions.    Others  note  no  stimulation  whatever. 

Reports  from  Washington31  and  Oregon1  corroborate  the  observa- 
tions made  in  California  on  the  absence  of  seed  injury  and  apparent 
stimulation  of  seedlings  by  copper  carbonate. 

STANDAEDS  OF  CHEMICAL  PUKITY  AND  PHYSICAL  FINENESS 
FOE  COPPEE  CAEBONATE  DUST 

Commercial  copper  carbonate  contains  to  a  small  extent  various 
foreign  ingredients  due  to  the  process  of  manufacture.  The  basis 
of  manufacture  consists  of  bluestone  (CuS04.5H20),  which  usually 
contains  a  small  quantity  of  iron,  a  survival  in  the  manufacture  of 
sulfuric  acid  from  iron  pyrites.  Sodium  carbonate  is  added  to  the 
copper  sulfate  solution,  with  the  result  that  the  copper  carbonate  is 
precipitated  and  the  soluble  sodium  sulfate,  a  product  of  the  reaction, 
is  washed  out,  thus  removing  the  sulfuric  acid  ion.  When  dried,  the 
resultant  powder  is  amorphous,  entirely  without  crystals  if  pure, 
and  greenish  in  color.  Blue  color  indicates  the  presence  of  copper 
sulfate  and  an  incomplete  product.  The  chemical  formula  appears 
to  be  as  follows:  CuC03.Cu(OH)2.  The  proportions  of  CuC03  and 
Cu(OH)2  vary  widely,  according  to  the  care  exercised  in  its  manu- 
facture. If  too  much  heat  is  applied,  carbon  dioxide,  added  as  sodium 
carbonate  (Na2C03),  is  driven  off  as  gas.  This  increases  the  propor- 
tion of  copper  hydrate  at  the  expense  of  the  copper  carbonate.  Still 
further  heating  decomposes  the  rather  unstable  copper  hydrate, 
leaving  as  a  result  inert,  dark  brown  copper  oxide.  The  commercial 
product  consists  of  a  basic  copper  carbonate,  amorphous  in  texture, 
very  stable  under  ordinary  conditions,  and  not  subject  to  deliquescence 
or  crystallization.  Copper  carbonate  is  listed  as  insoluble  in  pure 
water,  but  it  is  slowly  soluble  in  dilute  acids,  such  as  carbonic,  dicar- 
bonic,  and  undoubtedly  many  organic  acids  which  normally  occur 
in  the  soil.  It  is  this  quality  of  slow  but  certain  solubility  which 
enables  this  fungicide  to  exert  for  a  considerable  period  a  continuous 
repressive  and  lethal  effect  upon  germinating  bunt  spores  whether 
held  upon  the  seed  or  occurring  in  the  soil  in  the  immediate  vicinity 
of  the  seed. 


Bulletin    364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT 


555 


As  copper  carbonate  is  normally  manufactured  for  use  in  the 
arts,  and  not  for  fungicidal  purposes,  no  special  efforts  were  made 
to  standardize  its  chemical  and  physical  composition.  At  the  incep- 
tion of  the  experiments  with  copper  carbonate  dust,  variations  in  its 
chemical  and  physical  composition  were  noted.  These  variations  were 
reflected  in  its  efficiency  as  a  preventive  of  bunt.  Farmers  complained 
of  this  condition  and  requested  information  concerning  standards  of 

TABLE   10 

Chemical  Analysis  of  the  Four  Lots  of  Copper  Carbonate,  the 
Effectiveness  of  which  is  Eeported  in  Table  8 


Sample  Number 


Chemical  Analysis  in  Per  Cent 

Copper  (Cu)...,_ 

Carbon  dioxide  (C02) 

Hydroxylion  (OH) .* 

Sulfuric  anhydride  (S02) 

Iron  (Fe) 

Calcium  oxide  (CaO) 

Loss  on  ignition 

Insoluble  residue 


54.4 
19.4 
14.0 

0 

tr. 

v.sm. 

29.4 


53.8 
18.3 
14.4 

0 

0 
v.sm. 
30.3 
small 


46.6 
15.9 
16.3 

0 

0 
some' 
30.2 
small 


21 

8 

7 

27 

24 
21 


Recombined  as  Salts 


Copper  carbonate  (CuC03) 

Copper  hydrate  Cu  (OH)2 

Copper  sulfate  (CuS04) 

Basic  copper  carbonate  CuC03.Cu  (OH)2. 


54.6 

40.3 

0 

94.9 


51.5 
41.5 

0 
93.0 


44.8 
46.9 

0 
92.0 


24.3 
20.7 

0 
45.1 


Density — Physical  Fineness 
Pounds  per  cubic  foot 


28.12 


43.75 


76.25 


36.25 


1  Analyses  by  Prof.  M.  E.  Jaffa,  Harold  Goss  and  Thos.  B.  Swift. 
*  We  are  indebted  to  Prof.  M.  E.  Jaffa  and  Mr.  Harold  Goss  of  the  University 
of  California,  and  Mr.  Thos.  B.  Swift,  for  the  analyses  in  table  10. 


purity  and  efficiency.  Analyses  were  made  of  various  samples  of 
copper  carbonate  dust  sold  to  the  farmers.  Representative  samples 
were  tested  for  bunt  control  and  reported  in  table  8.  Chemical 
analyses  of  these  samples  are  given  in  table  10.* 

In  regard  to  bunt  control,  one  of  the  samples  (No.  3,  table  8)  gave 
poor  results.  This  sample  contained  but  slightly  less  copper  (No.  3, 
table  10)  than  those  samples  which  gave  good  results.  On  examin- 
ation it  was  found  to  be  gritty  and  to  contain  crystals  blue  in  color. 
Zinc  oxide  was  present  in  considerable  quantities,  together  with  quan- 


556  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

tities  of  soluble  chlorides  and  other  salts.  Sample  No.  4  contained 
sulfates  in  large  quantities,  apparently  in  the  form  of  calcium  sulfate. 
The  calcium  sulfate  may  have  resulted  from  the  peculiar  processes 
of  manufacture,  or  from  addition  of  calcium  sulfate  as  a  dilutant. 
As  has  been  shown  in  numerous  experiments  (table  7),  the  addition 
of  various  quantities  of  lime  (CaC03)  or  gypsum  (CaS04.2H20) 
caused  a  corresponding  reduction  in  efficiency  of  bunt  control.  The 
addition  of  dilutants  appears  to  be  a  practice  of  doubtful  value.  The 
results  indicate  that  the  farmer  should  use  the  best  and  purest  copper 
carbonate  dust  obtainable,  even  at  an  increase  in  price  over  less 
efficient  and  less  costly  copper  carbonate  compounds. 

It  is  difficult  to  increase  copper  carbonate  in  basic  copper  car- 
bonate beyond  55  per  cent.  By  comparing  the  per  cent  of  this  copper 
carbonate  with  copper  in  satisfactory  samples,  it  is  seen  that  copper 
and  copper  carbonate  are  approximately  equal.  Wide  departures 
from  this  proportion  should  be  carefully  scrutinized. 

The  first  three  samples  of  copper  carbonate  dust  employed  in  the 
experiments  in  table  8  contained  sufficient  quantities  of  copper  to 
insure  good  results,  judging  by  comparative  analyses  (table  10). 
However,  No.  3  gave  poor  bunt  control.  On  examination,  its  physical 
condition  was  found  to  be  poor — that  is,  the  particles  were  coarse, 
and  the  fine,  silky  feeling  common  to  the  best  samples  was  lacking. 
This  led  to  the  examination  of  fineness  of  the  particles  of  copper 
carbonate  dust  in  order  to  arrive  at  a  reasonable  standard  for  fineness. 
The  results  of  the  physical  analyses  of  four  samples  tested  in  table  8 
are  reported  in  table  10. 

In  determining  the  physical  condition  of  copper  carbonate  dusts, 
two  tests  were  found  necessary:  (1)  the  determination  of  the  density 
(weight  of  a  given  volume)  of  the  dust,  and  (2)  the  fineness  of  the 
dust  particles.  The  density  was  determined  by  shaking  down  a  given 
weight  in  a  measured  cylinder,  and  the  fineness  by  passing  the 
material  through  a  200-mesh  sieve  while  in  aqueous  suspension.  By 
these  tests  those  samples  which  gave  the  best  control  of  bunt  were 
found  to  average  about  31  pounds  per  cubic  foot.  Over  99  per  cent 
of  this  material  passed  through  the  200-mesh  sieve.  On  the  other 
hand,  it  should  be  noted  that  the  copper  carbonate  (sample  No.  3, 
table  8)  which  gave  the  poorest  bunt  control  returned  the  highest 
density,  78.84  pounds  per  cubic  foot,  with  reduced  quantities,  91.85 
per  cent  passing  through  the  200-mesh  sieve  (sample  No.  3,  table  10). 
As  the  amount  of  copper  (47.3  per  cent)  was  not  too  low  for  fair 
results,  the  lack  of  bunt  control  may  be  charged  to  the  excessive 
density  and  coarseness  of  the  material,  i.e.,  poor  physical  condition. 


Bulletin   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT  557 


SUGGESTED  QUALITIES  FOR  A  STANDARD  COPPER  CARBONATE 

With  a  method  as  new  as  the  copper  carbonate  dust  treatment, 
it  is  difficult  to  fix  a  standard  for  chemical  and  physical  qualities.  The 
experiments  conducted  at  Davis,  and  the  reports  from  farmers  over 
the  Pacific  Coast  States,  indicate  the  necessity  for  an  approximate 

TABLE  11 

Comparison  of  the  Per  Cent  of  Copper  in  a  Number  of  Commercial  Lots 

of  Copper  Carbonate 


Basic 

Sample 
No. 

Copper 

(Cu) 
Per  Cent 

Copper 
carbonate 
(CuC03) 
Per  Cent 

Copper 

hydrate 

(Cu(OH)2) 

Per  Cent 

Copper 

sulfate 

(CuS04) 

Per  Cent 

Calcium 
oxide 
(CaO) 

Per  Cent 

Iron 

(Fe) 

Per  Cent 

copper 
carbonate 
CuC03.Cu 

(OH)  2) 
Per  Cent 

Density 
lbs   per 
cubic  ft. 

1 

54.37 

54.14 

39.93 

.30 

.48 

94.07 

30.90 

2 

53.12 

51.76 

46.81 

.76 

98.57 

3 

55.80 

54.97 

43.46 

.57 

98.43 

4 

50.80 

3.81 

55.81 

39.81 

.75 

2.30 

59.62 

5 

47.32 

60.38 

23.59 

5.90  (3) 

.81 

.47 

83.97 

78.84 

6 

12.85 

29.73 

23.54 

35.70 

36.410) 

.35 

53.27 

34.71 

7 

21.90 

25.01 

19.74 

15.55 

24.33 

.54 

44.75 

31.88 

8 

55.80 

65.41 

34.01 

.65 

99.42 

9 

53.24 

8.87 

48.78 

42.57 

.56 

.66 

57.65 

55.82 

10 

51.88 

1.19 

93.70 

11 

55.58 

65.41 

33.69 

.65 

99.10 

12 

54.11 

55.75 

39.05 

tr. 

.56 

94.80 

13 

54.40 

54.61 

40.38 

v.  small 

tr. 

94.99 

28.12 

14 

53.80 

51.51 

41.50 

v.  small 

92.01 

43.75 

15 

53.30 

51.48 

40.55 

small 

92.03 

35.00 

16 

46.60 

48.80 

46.95 

some 

95.75 

76.25 

17 

50.60 

52.61 

40.47 

small 

93.08 

62.50 

18 

53.80 

52.35 

38.92 

v.v. small 

tr. 

91.27 

51.25 

19 

21.30 

24.38 

20.75 

v.lge(2) 

.73 

45.13 

36.25 

20 

52.90 

53.68 

39.20 

large 

92.88 

66.35 

Copper  average  in  12  uniform  samples 55.30  per  cent 

Copper  carbonate  average  for  the  same  12  samples 53.96  per  cent 

Copper  hydrate  average  for  the  12  samples 39.83  per  cent 

1  The  calcium  oxide  combined  as  calcium  carbonate  in  this  mixture. 

2  The  calcium  oxide  is  here  combined  as  barium  sulfate  in  large  proportions. 

3  This  material  is  zinc  oxide  which  may  be  combined  as  zinc  sulfate. 


standard.  The  results  of  experiments  reported  in  tables  10  and  11 
indicate  that  the  following  qualifications  for  copper  carbonate  dust 
may  be  required  without  materially  adding  to  the  cost  of  manu- 
facture, but  which  will  at  the  same  time  provide  the  farmer  with 
an  effective  copper  carbonate  dust: 


558 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


1.  Copper  carbonate  dust  should  consist  of  51  to  54  per  cent  of 
CuC03  and  39  to  42  per  cent  of  Cu(OH)2.  The  former  may  range 
from  50  to  60  per  cent,  and  the  latter  from  35  to  48  per  cent  of  the 
dust,  but  best  results  may  be  anticipated  from  the  more  regular  com- 
position.    The  combination  of  CuC03.Cu(OH)2  should  comprise  94 


Fig.  5. — California  Dusting  Machine,  front  view. 

per  cent  of  the  fungicide,  but  may  vary  from  92  to  98  per  cent  for 
good  material. 

2.  Copper  should  not  be  less  than  50  per  cent,  may  average  53 
per  cent  to  advantage,  and  may  rise  to  55  per  cent  of  the  dust.  It 
should  be  found  solely  in  the  carbonate  and  hydrate  forms  and  not 
as  sulfates  or  oxide. 


BULLETIN    364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT 


559 


3.  Inert  or  foreign  matter  may  include  iron,  silica,  and  slight 
amounts  of  sodium  sulfate  and  non-fungicidal  material  not  to  exceed 
6  or  7  per  cent. 


Fig-.  6. — California  Dusting  Machine,  rear  view. 


4.  Copper  carbonate  dust  should  not  be  of  greater  density  than 
32  pounds  per  cubic  foot  when  shaken  down  in  a  graduated  tube. 
Lower  density  is  desirable. 

5.  Not  less  than  99  per  cent  of  the  copper  carbonate  dust  in 
aqueous  suspension  should  pass  through  a  200-mesh  sieve. 


560 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


MACHINES  FOE  APPLYING  COPPER  CARBONATE  DUST 

In  Australia  copper  carbonate  dust  has  given  good  results,7'  8> 9- 10 
but  has  not  been  used  extensively  except  by  small  farmers.  This,  it 
is  stated,  is  due  to  the  lack  of  proper  machinery  for  applying  the 
dust  thoroughly  and  economically  to  large  quantities  of  seed. 


7. — California  dusting  machine.     Side  view  showing  sprockets  and  opening 
Dden  container. 


Fig.  < . — v^fcui 
to  the  wooden  container. 


The  barrel  churn  has  been  used  where  small  lots  are  treated.  A 
modification  of  the  barrel  churn,  or  concrete  mixer,  has  been  put 
out  by  the  Division  of  Agronomy  of  the  University  of  California 
Experiment  Station.    This  machine  is  a  modification  of  the  Washing- 


BULLETIN    364]         FUNGICIDAL   DUSTS   FOR   THE    CONTROL    OF   BUNT 


561 


ton  State  College  smut  treating  machine.14  It  is  constructed  almost 
entirely  of  wood  and  can  be  made  on  the  farm  with  common  tools  if 
the  wheels  and  sprockets  for  tumbling  the  container  be  provided. 
It  has  a  capacity  of  one  sack  of  seed  wheat  every  five  minutes.  Two 
minutes  are  required  to  mix  the  seed  and  dust  and  three  minutes  for 
filling,  emptying  and  charging  with  the  dust.  Blueprints  of  this 
machine  may  be  secured  from  the  Agricultural  Extension  Service 
Division,  at  Berkeley. 


to'WSC  plan 


Fig.  8. 


-California  dusting  machine.     Diagram. 


UNIVERSITY,?  CALIFORNIA 
COLLEGE:   „  AGRICULTURE 

B£XK£L.£  Y.        CAC/FOAH/A 

SMUT  TREATING  MACWA/E 

•Scale     /^  m  =/rr- 


/Vox  /,  /9ZZ 


Machines  patterned  after  the  automatic  screw  elevator  type  of 
machine,  such  as  used  in  whitening  smutty  or  dark  colored  barley 
at  the  large  exporting  warehouses,  are  in  use.  This  type  of  machine 
automatically  receives  the  seed  and  dust,  mixing  them  in  the  passage 
of  the  seed  through  the  enclosed  screw  elevator,  but  the  loss  of  dust 
into  the  air  is  detrimental  to  workers. 

A  very  successful  automatic  duster  is  in  use  at  Westhaven,  Fresno 
County.  The  principle  on  which  the  process  depends  consists  in 
gravity  action  operating  as  the  seed  is  received  from  the  cleaner  and 
grader.  Copper  carbonate  dust  is  automatically  blown  into  the  top 
of  the  machine  and  is  sucked  down  through  it  by  means  of  a  fan 
driven  by  a  %  h.p.  electric  motor.  Baffle  boards  tumble  the  descend- 
ing  grain,    mixing   it   thoroughly   with   the    fungicidal    dust.      This 


562 


UNIVERSITY    OF   CALIFORNIA — EXPERIMENT    STATION 


machine  is  simpler  than  the  others  and  far  less  costly  in  construction. 
It  is  air-tight,  being  made  of  tongue  and  groove  lumber.  No  dust 
escapes  except  at  the  sack  filler,  and  here  in  such  small  quantities 
that  the  operator  does  not  require  a  mask.  In  size  it  is  116  inches 
high,  and  36  inches  by  19  inches  for  the  cross  section.     It  is  designed 


SEED   CONDITIONER   AND   DUSTER   APPARATUS 


Fig.  9. — Universal  duster.  Cleaned 
and  graded  seed  received  at  the  upper 
end.  The  dust  is  mixed  by  gravity 
and  a  forced  blast.  Capacity:  150  to 
300  bushels  per  hour.  No  dust  mask 
was  required  when  the  machine  "was 
well  fitted  and  thoroughly  varnished 
to  fill  all  cracks. 


Frederick  Steigmeyer,  Inventor.      Patent  applied  for. 

Fig.  10. — Diagram  of  the  Universal  dust- 
ing machine. 


to  thoroughly  dust  150  bushels  per  hour,  but  can  be  adjusted  to 
double  this  capacity.  When  used  in  connection  with  seed  cleaning 
machinery,  no  extra  help  is  required,  as  the  grain  may  either  be 
sacked  or  elevated  to  a  bin  and  stored  awaiting  seeding  time.  This 
type  of  dusting  machine  should  be  very  serviceable  in  connection  with 
grain  elevators  or  warehouses  where  seed  is  cleaned,  graded  and  sold. 
A  centralized  treating  plant  equipped  with  such  a  machine  might 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT  563 

well  be  operated  by  the  farm  bureau  or  similar  organizations.  With 
little  or  no  additional  expense  beyond  the  cost  of  the  copper  carbonate 
dust,  seed  wheat  may  be  treated  ready  for  seeding  at  time  of  cleaning. 
Automatic  seed  treatment  by  this  method  should  cheapen  this  process 
much  below  the  cost  to  the  farmer  under  ordinary  farm  operations. 
Loss  of  time  may  be  eliminated  at  the  seeding  season  by  treating  the 
seed  in  advance  since  no  seed  injury  results  from  storing  seed  treated 
with  copper  carbonate  dust.14 

It  is  hoped  that  this  dusting  of  seed  wheat  with  copper  carbonate 
dust  by  automatically  operated  machinery  will  lead  to  universal  seed 
treatment.  If  such  practices  could  be  put  continuously  into  effect, 
there  is  evidence  that  bunt  might  be  reduced  to  a  small  minimum, 
and  in  many  areas  entirely  eliminated. 

EFFECT  OF  COPPER  CARBONATE  DUST  UPON  OPERATORS 

Many  complaints  have  been  received  concerning  the  nauseating 
effect  of  copper  carbonate  dust  when  inhaled.  In  some  instances 
farmers  have  reverted  to  the  liquid  treatment  of  seed  wheat,  even 
though  the  copper  carbonate  method  is  preferable,  because  of  this 
irritating  quality  of  the  dust.  In  the  process  of  manufacture  it 
causes  the  same  trouble,  but  the  use  of  masks  permits  the  operators 
to  work  indefinitely  in  its  presence  without  injury.  The  mask  found 
to  give  the  best  service  at  these  plants  (fig.  11)  depends  in  one  form 
upon  a  wet  sponge  for  its  effectiveness  and  in  the  other  on  a  dry  filter 
paper.  Both  are  light  and  permit  easy  breathing  and  ordinary  con- 
versation while  working.     The  cost  retail  is  $1.75  and  $2.00  each. 

If  the  worker  cannot  secure  a  mask,  it  is  possible  to  avoid  con- 
siderable dust  irritation  by  tying  a  wet  bandana  handkerchief  or 
similar  cloth  over  the  nose  and  mouth. 

Although  no  feeding  tests  have  been  made,  it  does  not  seem  advis- 
able to  feed  wheat  which  has  been  treated,  because  copper  carbonate 
is  poisonous. 

DEMONSTRATIONS  WITH  COPPER  CARBONATE  DUST  ON  FARMS 

Many  demonstrations  were  made  on  California  grain  farms  in 
1921. 24  In  1922,  cooperative  demonstrations  were  made  in  eighteen 
counties,  under  the  direction  of  farm  advisors  or  county  agents. 
Almost  15,000  acres  were  sown  with  copper  carbonate  dusted  seed. 
Similar  demonstrations  were  held  in  Washington31  and  Oregon.1  The 
results  secured  for  the  1922  harvest  in  these  three  Pacific  Coast  states 
are  recorded  in  table  12. 


564 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


The  control  of  bunt  by  copper  carbonate  dust,  as  shown  in  the 
records  of  table  12,  indicate  that :  in  California  it  is  almost  completely 
effective;  in  Washington,  more  so  than  other  fungicides;  and  in 
Oregon,  as  efficient  as  bluestone.     Since  bluestone,  bluestone-lime,  and 


iiSffy-fU'.  w 


Fig.  11. — An  effective  device  which 
carbonate  dust. 


successfully  prevents  inhalation  of  copper 


formaldehyde  are  recognized  preventives  of  infection  from  seed- 
borne  spores,  the  lack  of  complete  control  denotes  either  that  the  seed 
was  too  heavily  smutted  or  that  the  attack  came  from  bunt-infested 
soil  and  was  therefore  beyond  the  reach  of  fungicides  applied  to  the 
seed.  The  details  of  these  investigations  are  reported  in  the  discussion 
which  follows. 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT 


565 


A  critical  point  in  bunt  control  lies  in  the  thorough  application 
of  the  copper  carbonte  dust  to  the  seed.  Lack  of  intimate  mixing 
has  been  reported  as  the  cause  for  lack  of  better  control.  So  tenacious 
are  the  small  amorphous  particles  of  copper  carbonate  that  with  a 
low  power  microscope  they  are  seen  to  adhere  to  every  portion  of  the 
seed  coat  in  a  manner  not  unlike  that  of  the  bunt  spores  themselves. 
Even  when  dusted  seed  wheat  is  sown  by  the  broadcast  seeder,  the 
particles  of  copper  carbonate  dust  still  adhere  to  all  parts.     In  the 

TABLE  12 

Summary  of  Bunt  Control  Tests  with  Copper  Carbonate  in  the 
Pacific  Coast  States  for  the  1922  Harvest 


Counties  reporting 

Farms  reported 

Bunt,  untreated  seed 

Bunt,  bluestoned  seed 

Bunt,  bluestone-limed  seed 

Bunt,  formaldehyded  seed 

Bunt,  formaldehyde-lime  seed. 
Bunt,  copper  carbonate 


Washington  0) 


Num- 
ber 
trials 


9 
75 

8 
28 
10 
33 

3 
75 


Bunt 
per 

cent 


93.7 
10.7 
9.0 
6.9 
6.6 
5.4 


Oregon  0) 


Num- 
ber 
trials 


31 
0 

17 
1 

14 
0 

31 


Bunt 
per 
cent 


0.0 
2.4 
0.0 
0.8 
0.0 
2.3 


California 


Num- 
ber 
trials 


18 

40 

31 

16 

7 

8 

0 

35 


Bunt 
per 
cent 


6.0 
3.0 
2.0 
2.0 
0.0 
.6 


1  These  tests  were  conducted  under  the  supervision  of  county  agents  and 
reported  for  Oregon  by  Prof.  H.  P.  Barss,1  Plant  Pathologist,  Oregon  Agricultural 
Experiment  Station,  and  for  Washington  by  Prof.  George  L.  Zundel,28  Extension 
Plant  Pathologist  of  the  Washington  State  College. 


drill,  friction  removes  bnt  little  of  the  dust,  and  in  addition  any 
excess  dust  over  that  held  by  the  seed  coat  is  sown  with  the  seed, 
adding  to  its  effectiveness. 

Farmers  have  complained  of  poor  bunt  control  by  copper  car- 
bonate compounds  lacking  in  physical  fineness  and  chemical  purity 
similar  to  the  qualifications  set  forth  in  table  10. 

The  absence  of  germ  injury  to  seed  wheat  treated  with  copper 
carbonate  has  been  conclusively  demonstrated  by  hundreds  of  care- 
fully controlled  tests.  Everywhere  farmers  have  observed  the  same 
results.  While  complaints  of  seed  injury  caused  by  formaldehyde 
and  bluestone  treatments  have  been  frequent,  none  have  been  received 
against  copper  carbonate.  According  to  the  reports  from  county 
agents  on  the  Pacific  Coast,  the  percentage  of  plants  per  acre  for 
copper  carbonate-treated  seed,  compared  with  other  seed  treatments, 


566  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

is  greater  by  30  to  50  per  cent,  but  in  many  cases  the  range  is  much 
greater.  Occasionally  some  farmer  complains  of  too  thick  a  stand 
from  copper  carbonate  treated  seed.  Certainly  a  better  stand  is 
secured  from  copper  carbonate-treated  seed  than  from  seed  treated 
with  either  bluestone  or  formaldehyde-treated  seed  sown  at  the  same 
rate. 

Many  farmers  report  that  the  copper  carbonate-dusted  seed 
sprouted  several  days  ahead  of  seed  otherwise  treated,  or  untreated. 
When  these  fields  have  been  contrasted,  the  differences  are  quite 
evident.  Stimulation  of  seedlings  by  copper  carbonate  frequently 
pushes  them  out  of  the  soil  before  crusts  form  to  delay  emergence. 
Thicker  stands  have  caused  weed  suppression  and  increased  yields. 
The  majority  of  the  farmers  who  used  copper  carbonate  dust  in  1922 
report  better  yields  from  fields  sown  with  dusted  seed  than  from 
fields  sown  with  seed  treated  by  liquid  fungicides,  or  from  fields  sown 
with  untreated  seed. 

Farm  tests  are  more  or  less  variable,  owing  to  variations  in  appli- 
cation of  the  fungicide  and  the  spore  load.  Soil  infestation  by  bunt 
spores  also  disturbs  bunt  control.  The  application  of  copper  car- 
bonate dust  will  undoubtedly  be  improved  when  serviceable  dusting 
machinery  is  available. 

It  is  not  to  be  expected  that  this  dust  fungicide  will  give  better 
control  of  seed-borne  bunt  than  the  standard  solutions,  but  that  it 
will  equal  them  in  this  respect  except  when  the  seed  is  blackened 
with  bunt  spores.  Though  the  control  of  bunt  by  copper  carbonate 
is  no  better  than  with  the  standard  fungicide,  the  increase  in  the 
number  of  plants  and  heads  per  acre  has  resulted  in  better  yields. 
These  outstanding  advantages  following  the  use  of  copper  carbonate 
should  result  in  the  general  adoption  of  this  dust  fungicide  as  a 
bunt  preventive. 

SOURCES  OF  COPPER  CARBONATE 

Difficulty  in  securing  copper  carbonate  in  sufficient  quantities  has 
been  encountered.  If  the  use  of  this  fungicide  is  to  become  general, 
then  sufficiently  large  supplies  should  be  available  to  meet  all  needs. 
Three  sources  of  supply  exist:  (1)  importations  from  Germany;  (2) 
manufacturers  on  the  Atlantic  seaboard;  and  (3)  local  manufacturers. 
The  copper  carbonate  from  abroad  and  from  eastern  sources  is  manu- 
factured for  the  metallic  arts  and  not  for  use  as  a  dust  fungicide, 
and  it  may  be  at  times  too  coarse  for  entirely  successful  control  of 
infection  from  seed  borne  spores.     No  doubt  this  difficulty  can  be 


BULLETIN   364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT  567 

remedied  if  special  orders  are  placed  for  copper  carbonate  of  a  speci- 
fied physical  quality  and  chemical  purity.  In  the  San  Francisco  bay 
region  three  or  four  chemical  concerns  are  now  manufacturing  copper 
carbonate  dust  for  use  as  a  fungicide.  By  consultation  with  these  firms 
the  specifications  for  the  qualities  of  effective  copper  carbonate  have 
become  understood,  and  improvement  in  the  quality  of  the  fungicide 
put  out  has  followed.  Owing  to  the  comparative  newness  of  the  dust 
method  for  bunt  control,  manufacturers  are  reluctant  to  create  large 
stocks  which  may  remain  unsold.  Many  farmers  complain,  however, 
that  they  have  had  to  treat  their  seed  by  the  old  methods  for  lack  of 
supplies  of  copper  carbonate.  In  1920,  only  a  few  ounces  were  used ; 
in  1921,  about  12,000  to  15,000  acres  were  sown  with  treated  seed ;  but 
in  1922,  estimates  place  the  acreage  at  more  than  250,000. 


SUMMARY 

1.  Many  fungicidal  solutions,  though  destructive  to  bunt  spores 
on  the  seed,  injure  and  destroy  seed  germs.  Distorted  plants,  delayed 
growth,  and  poor  stands  frequently  occur.  Bluestone  represses  root 
growth,  and  formaldehyde  represses  plumule  development. 

2.  All  poor  stands  are  not  caused  by  seed  treatment,  for  soil  and 
weather  conditions  prevent  a  large  jjortion  of  the  seed  from  develop- 
ing into  seedlings.  A  reduction  of  germination  to  almost  50  per  cent 
occurs  commonly  on  the  University  Farm  at  Davis,  California 
(table  9). 

3.  Seed  treated  by  fungicidal  solutions  showed  reductions  in  germ- 
ination in  the  soil  when  compared  with  laboratory  germinations  in  112 
tests  as  follows : 

Formaldehyde  96.3  to  41.5  per  cent 

Bluestone  38.1  to  31.4  per  cent 

Bluestone-lime  73.6  to  39.6  per  cent 

4.  Flowers  of  sulfur  reduced  bunt  to  about  one-tenth  of  the  infec- 
tion which  occurred  in  similar  unsulfured  seed  even  where  the  dosage 
of  smut  spore  was  light.    Sulfur  is  not  a  dependable  bunt  fungicide. 

5.  The  amount  of  bunt  in  a  crop  depends  in  large  part  upon  the 
quantity  of  bunt  spores  borne  by  the  kernel.  The  per  cent  of  bunt 
decreases  with  the  spore  dosage. 

6.  Bluestone  powder  applied  to  seed  at  the  rate  of  two  or  three 
ounces  per  bushel  is  almost  as  effective  as  copper  carbonate  in  con- 
trolling bunt  infection.     The  difficulty  of  its  use  lies  in  the  fact  that 


568  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 

it  may  not  retain  its  powdered  form  because  it  becomes  massed  by 
absorbing  moisture.  Therefore,  if  copper  carbonate  dust  is  not  avail- 
able, bluestone  powder  or  anhydrous  copper  sulfate  may  be  used  as 
a  fair  substitute. 

7.  Copper  carbonate  dust  applied  to  seed  wheat  at  the  rate  of 
two  ounces  or  more  to  the  bushel  effectively  controls  bunt  when  the 
seed  is  not  blackened  with  spores.  For  heavily  bunted  seed,  bluestone 
and  formaldehyde  solutions  are  more  effective,  but  are  liable  to  cause 
severe  seed  injury. 

8.  Seed  wheat  treated  with  copper  carbonate  dust  is  not  injured 
by  the  fungicide  even  when  held  in  storage  for  an  indefinite  period. 
This  permits  the  treating  of  seed  during  the  slack  season,  thus  avoid- 
ing loss  of  valuable  time  during  seeding  operations. 

9.  Germination  of  seed  wheat  is  not  inhibited  by  copper  carbonate 
dust.  Excellent  stands  usually  are  secured  and  less  seed  required 
per  acre  than  when  fungicidal  solutions  are  used.  Seed  treated  by 
the  standard  liquid  methods  frequently  have  to  be  sown  30  to  70 
per  cent  heavier  than  is  necessary  for  copper  carbonate-dusted  seed 
(table  9). 

10.  Seed  treated  with  copper  carbonate  dust  germinates  earlier 
and  makes  a  more  vigorous  seedling  growth  than  seed  treated  with 
fungicidal  solutions.  Prompt  emergence  from  the  soil  and  early  root 
development  combined  with  a  superior  stand  are  usually  reflected  in 
an  increased  yield. 

11.  Dilution  of  copper  carbonate  dust  does  not  appear  to  be 
warranted  because:  (1)  only  a  limited  quantity  can  be  retained  upon 
the  surface  of  the  seed  (less  than  two  ounces  per  bushel)  ;  (2)  diluted 
copper  carbonate  dust  applied  at  two  ounces  per  bushel  is  not  com- 
pletely effective  in  bunt  control;  and  (3)  dilutions  may  favor  poor 
processes  in  manufacture,  resulting  in  inferior  bunt  control  (table  6). 

12.  The  best  standard  for  effective  copper  carbonate  dust  appears 
to  be  as  follows : 

Copper  in  the  form  of  copper  carbonate  (52  to  54  per  cent) 
and  copper  hydrate  (39  to  42  per  cent),  totaling  93  to  94  per 
cent  of  these  two,  with  impurities  amounting  to  6  or  7  per  cent 
of  the  whole  mass. 

Fineness :  Ninety-nine  per  cent  in  aqueous  solution  should 
pass  through  a  200-mesh  sieve. 

Density  after  shaking  down  dry :  not  over  32  lbs.  per  cubic 
foot. 

Color:  light  green,  never  blue. 


Bulletin    364]         FUNGICIDAL   DUSTS   FOR   THE   CONTROL   OF   BUNT  569 

13.  Copper  carbonate  dust  when  inhaled  causes  nausea  and  other 
forms  of  irritation.  These  inconveniences  can  be  avoided  by  wearing 
a  dust  mask  as  prescribed  by  law  for  workers  in  factories  producing 
this  and  other  chemical  dusts.  A  wet  sponge  or  wet  handkerchief  tied 
over  the  nose  and  mouth  will  give  considerable  relief. 

14.  A  serious  drawback  to  the  extension  of  the  copper  carbonate 
dust  treatment  lies  in  the  limited  supply  of  the  chemical.  It  may  be 
imported,  but  it  is  then  likely  not  to  comply  with  the  standards  of 
fineness  and  purity  demanded.  A  limited  number  of  factories  are 
now  producing  satisfactory  copper  carbonate  dust  in  the  San  Fran- 
cisco bay  region. 

15.  The  price  of  copper  carbonate  usually  is  more  than  double 
that  of  bluestone.  As  copper  carbonate  contains  more  than  double 
the  amount  of  copper  (52-55  per  cent)  contained  in  bluestone  (25.04 
per  cent),  from  which  it  is  made,  this  ratio  is  not  unreasonable.  How- 
ever, the  saving  in  the  cost  of  labor  with  the  dust  treatment  is  many 
times  greater  than  this  difference  in  price. 

16.  The  greatest  obstacle  to  the  universal  adoption  of  copper 
carbonate  dust  lies  in  the  lack  of  proper  machinery  to  dust  econom- 
ically and  effectively  large  quantities  of  seed  in  a  short  time.  This 
difficulty  is  rapidly  being  overcome  by  the  invention  of  automatic 
ducting  machinery.  This  machinery  should  properly  become  part  of 
the  local  warehouse  or  elevator  where  seed  may  be  cleaned,  graded 
and  dusted  at  one  operation,  and  stored  ready  for  use. 

17.  A  few  reports  unfavorable  to  the  use  of  copper  carbonate 
have  come  from  other  regions,16  but  in  the  great  majority  of  instances 
the  reports  have  been  very  satisfactory.  Reports  are  now  available 
from  Australia,  Canada,  Denmark,  Italy,  and  several  parts  of  the 
United  States.5- 13- 19> 25 

18.  Organic  mercuric  fungicides,  usually  consisting  of  chlor- 
phenol-mercuric  compounds  in  varying  porportions,  have  been  found 
to  be  excellent  bunt  preventives  without  germ  injury  when  used  as 
solutions,  but  less  effective  when  applied  as  dusts.  These  compounds : 
Chlorophol,12'  27> 28  Seedosan,  Germisan,  etc.,  are  not  readily  available 
and  are  apparently  very  expensive. 

19.  All  seed  wheat  should  be  treated  every  year  because  a  slight 
quantity  of  bunt  spores  may  cause  wholesale  infection,  as  each  bunted 
kernel  or  gall  contains  from  one  to  eight  million  spores.4 


570  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


LITERATURE  CITED 

i  Barss,  H.  P.  Results  of  tests  with  copper  carbonate.  Harvest  of  1922.  Pre- 
liminary Report.     Oregon  Agric.  Exp.  Sta.,  Circ.  30.     August  10,  1922. 

2  Bolley,  H.  L.  The  use  of  the  centrifuge  in  diagnosing  the  plant  diseases.  Proc. 
Soc.  for  the  Prom,  of  Agric.  Sci.,  23:82-85.     1902. 

s  Bolley,  H.  L.  New  work  upon  the  smuts  of  wheat,  oats,  and  barley,  and  a 
resume  of  the  treatment  experiments  for  the  last  three  years.  No.  Dak. 
Agric.  Exp.  Sta,  Bull.  27.     1897. 

4  Cobb,   N.   A.     Quantitative  estimation  of  bunt  spores   in  seed  wheat.     Agric. 

Gazette,  New  South  Wales,    16:1113-1117.     1905. 

5  Coons,  G.  H.     Copper-dust  treatment  for  stinking  smut.     Michigan  Quarterly 

Bull.,  5:1,  pp.  8-11.     August,  1922. 

6  Darnell-Smith,  G.  P.,  and  Carne,  W.  M.     Effect  of  formalin  on  germination 

of  plants.     In  3rd  Rept.  Gov't.  Bull.  Microbiol.  N.  S.  W.     1912. 

7  Darnell-Smith,  G.  P.     The  use  of  copper  carbonate  as  a  fungicide.     Agric. 

Gazette,  N.  S.  W.,  26   (1915),  No.  3,  p.  242. 
s  Darnell-Smith,   G.   P.     The  prevention   of  bunt.     Experiments   with   various 

fungicides.     Agric.  Gazette,  N.  S.  W.,  28:185-189.     March  2,  1917. 
9  Darnell-Smith,  G.  P.,  and  Ross,  H.    A  dry  method  of  treating  seed  wheat  for 

bunt.     Agric.  Gazette,  N.  S.  W.,  30:685-692.     1919. 
io  Darnell-Smith,  G.  P.     Fungicidal  dusts  for  control  of  smut.     Agric.  Gazette, 

N.  S.  W.,  32:796-798.     1921. 
ii  Darnell-Smith,  G.  P.     Dry  copper  carbonate  for  bunt.     Agric.  Gazette,  N.  S. 

W.,  33  (1922),  No.  10,  pp.  754-755. 
12  Heald,  P.  D.     Div.  of  Plant  Pathology.     Wash.  Coll.   Sta.  Bull.   167    (1922), 

pp.  38-43. 
is  Heald,  F.  D.,  and  Smith,  L.  J.     The  dusting  of  wheat  for  bunt  or  stinking 

smut.     Wash.  Agric.  Exp.  Sta.  Bull.  168,  p.  15.     June,  1922. 
14  Heald,  F.  D.,  and  Smith,  L.  J.     The  dusting  of  wheat  for  bunt  or  stinking 

smut.     Wash.  State  Coll.  Agric.  Exp.  Sta.  Bull.  171.     October,  1922. 
is  Heald,  F.  D.     The  relation  of  spore  load  to  the  per  cent  of   stinking  smut 

appearing  in  the  crop.     Phytopath.,  11:269-278.     1921. 

16  Hungerford,  C.  W.     The  News  Letter.     The  University  of  Idaho.     Published 

by  the  College  of  Agric.    Vol.  8,  No.  8.    September  25,  1922. 

17  Hurd,  Annie  May.     Injury  to  seed  wheat  from  drying  after  disinfection  with 

formaldehyde.     Jour.  Agric.  Res.,  V,  No.  3.     November  1,  1920. 
is  Hurd,  Annie  May.    Seed-coat  injury  and  viability  of  seeds  of  wheat  and  barley 

as  factors  in  susceptibility  to  molds  and  fungicides.     Jour.  Agric.  Rec,  Vol. 

21,  No.  2.     April  15,  1921. 
is  KiJHN,  J.  G.     Krankheit  die  Kulturgewachse,  p.  85,  1859. 
20  Lambert,  E.  B.,  and  Bailey,  D.  L.     Results  of  treating  seed  of  spring  wheat 

and  oats  with  copper  carbonate  dust  to  prevent  smut.     Phytopath.,  12.     1922. 


BULLETIN   364]         FUNGICIDAL   DUSTS  FOR   THE   CONTROL   OF   BUNT  571 

21  Mackie,  W.  W.     Seed  treatments  for  the  prevention  of  cereal  smuts.     Cal.  Exp. 

Sta.  Cire.  214.     September,  1919. 

22  Mackie,   W.  W.,   and   Briggs,  F.   N.      Fungicidal   dusts  for   control   of   bunt. 

Science,  n.s.,  Vol.  52,  No.  1353,  pp.  540-541.     December  3,  1920. 

23  Mackie,  W.  W.,  and  Briggs,  F.  N.     Chemical  dusts  for  the  control  of  bunt. 

Phytopath.,  11:38-39.     1921. 

24  McLeod,  George  E.     Control  of  smut.     Agric.  Dept.,  Sperry  Flour  Co.,  Stock- 

ton, Calif.     November  18,  1921. 

25  Morettini,  A.     Sulla  efficacia  dei  trattamenti  polverulenti  contro  la  "carie" 

del  frumento.  (Efficiency  of  powders  for  controlling  smuts  of  cereals.) 
Trans,  by  Theo.  Holm.  Stoz.  Sperim.  Agric.  Ital.,  Vol.  54,  pis.  7-10  (Mo- 
dena),  pp.  293-315.     1921. 

26  Perkins,  A.  J.     Eandom  agricultural  jottings.     Jour.  Dept.  Agric.  So.  Africa, 

23:287-290.     1919. 

27  Eiehm,  E.     Prufungeiniger  Mittel  zur  Bekampfung  des  Steinbrandes.      (Experi- 

ments with  some  fungicides  to  combat  bunt,  or  stinking  smut.)  Trans,  by 
Theo.  Holm.  Nitth.  aus  d.  Kais.  Biol.  Aust.  f.  Land.  u.  Forstwiss.  Noft.  14, 
Berlin,  pp.  8-9.     1913. 

28  Eemy,  Th.,  and  Vasters,  J.     Beobachtungen  ueber  chlorphenol-quecksilber  als 

Pflanzenschutzmittel.  (Observations  on  Chlorphenol-Mercury  as  a  Fungi- 
cide.) Trans,  by  Theo.  Holm.  Illust.  Landwirt  Zeitung,  34th  year,  Berlin, 
1914,  pp.  769-771. 

29  Tubeuf,  von  Eeg.  Eath,  Dr.  Freiherr,     Studien  ueber  die  Brandkrankheiten 

des  Getreides  und  ihre  Bekampfung.  Mit  1  Tafel  (VIII)  und  19  Testfiguren 
Arbeiten  aus  der  Biologischen  abcheilung  fur  Land-  und  Forstwithschoft  am 
Kaiserl.  Gesundheitsamte.    II  pt.  4,  Berlin.     1902. 

so  Wheeler,  W.  A.  Preliminary  experiments  with  vapor  treatments  for  the  pre- 
vention of  the  stinking  smut  of  wheat.  So.  Dakota  Agric.  Coll.  Exp.  Sta. 
Bull.  89.     November,  1904. 

3i  Zundel,  George  L.  Summary  of  copper  carbonate  treatment  for  the  control  of 
smut.  State  of  Washington  1922  Crop.  Wash.  Agric.  Exp.  Sta.  August  2, 
1922. 


572  UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  12. — No.  3,  bunted  Propo  head  and  bunt  gall.  No.  4,  normal  Propo  head 
and  kernel.  When  bunted  plants  are  supplied  with  an  excess  of  space,  light, 
moisture  and  plant  food,  the  disease  may  stimulate  excessive  growth  as  indicated 
here. 


STATION  PUBLICATIONS  AVAILABLE  FOR  FEEE  DISTRIBUTION 


BULLETINS 

No.  No. 

253.   Irrigation   and   Soil  Conditions   in   the  332. 

Sierra  Nevada  Foothills,  California.  334. 

261.  Melaxuma    of    the    Walnut,    "'Juglans 

regia."  335. 

262.  Citrus   Diseases   of   Florida   and   Cuba 

Compared  with  these  of  California.  336. 

263.  Size  Grades  for  Ripe  Olives. 

268.   Growing  and  Grafting  Olive  Seedlings.  337. 

270.  A  Comparison  of  Annual  Cropping,  Bi-  339. 
ennial  Cropping,  and  Green  Manures 

on  the  Yield  of  Wheat.  341. 

273.  Preliminary  Report  on  Kearney  Vine-  342. 

yard  Experimental  Drain.  343. 

275.  The  Cultivation  of  Belladonna  in  Cali-  344. 

fornia. 

276.  The   Pomegranate.  345. 

278.  Grain   Sorghums. 

279.  Irrigation  of  Rice  in  California.  346. 

280.  Irrigation  of  Alfalfa  in  the  Sacramento  347. 

Valley. 

283.  The  Olive  Insects  of  California.  348. 

285.  The  Milk  Goat  in  California.  349. 

286.  Commercial    Fertilizers. 

287.  Vinegar  from  Waste  Fruits.  350. 
294.   Bean    Culture   in    California.  351. 

297.  The  Almond  in   California.  352. 

298.  Seedless  Raisin  Grapes. 

299.  The  Use  of  Lumber  on  California  Farms.  353. 
304.  A  study  on  the  Effects  of  Freezes  on  354. 

Citrus   in   California.  355. 

308.  I.  Fumigation  with  Liquid  Hydrocyanic  356. 

Acid.  II.  Physical  and  Chemical  Prop- 
erties of  Liquid  Hydrocyanic  Acid.  357. 

312.  Mariout  Barley. 

313.  Pruning  Young   Deciduous  Fruit  Trees. 

316.  The   Kaki  or  Oriental  Persimmon.  358. 
817.   Selections  of   Stocks  in  Citrus   Propa- 
gation. 359. 
319.  Caprifigs  and  Caprification.  360. 
821.   Commercial  Production  of  Grape  Syrup. 

324.  Storage  of  Perishable  Fruit  at  Freezing  361. 

Temperatures. 

325.  Rice  Irrigation  Measurements  and  Ex-  362. 

periments     in      Sacramento      Valley,  363. 

1914-1919. 
328.   Prune  Growing  in  California.  364, 

331.  Phylloxera-Resistant  Stocks. 


Walnut  Culture  in  California. 

Preliminary  Volume  Tables  for  Second- 
Growth  Redwoods. 

Cocoanut  Meal  as  a  Feed  for  Dairy 
Cows  and  Other  Livestock. 

The  Preparation  of  Nicotine  Dust  as 
an  Insecticide. 

Some  Factors  of  Dehydrater  Efficiency. 

The  Relative  Cost  of  Making  Logs  from 
Small    and    Large   Timber. 

Studies  on  Irrigation  of  Citrus  Groves. 

Hog  Feeding  Experiments. 

Cheese  Pests  and  Their  Control. 

Cold  Storage  as  an  Aid  to  the  Market- 
ing  of  Plums. 

Fertilizer  Experiments  with  Citrus 
Trees. 

Almond    Pollination. 

The  Control  of  Red  Spiders  in  Decidu- 
ous Orchards. 

Pruning  Young  Olive  Trees. 

A  Study  of  Sidedraft  and  Tractor 
Hitches. 

Agriculture  in  Cut-over  Redwood  Lands. 

California  State  Dairy  Cow  Competition. 

Further  Experiments  in  Plum  Pollina 
tion. 

Bovine  Infectious  Abortion. 

Results  of  Rice  Experiments  in   1922. 

The  Peach  Twig  Borer. 

Observations  on  Some  Rice  Weeds  in 
California. 

A  Self-mixing  Dusting  Machine  for 
Applying  Dry  Insecticides  and 
Fungicides. 

Black  Measles,  Water  Berries,  and 
Related    Vine    Troubles. 

Fruit  Beverage  Investigations. 

Gum  Diseases  of  Citrus  Trees  in  Cali- 
fornia. 

Preliminary  Volume  Tables  for  Second 
Growth  Redwood. 

Dust  and  the  Tractor  Engine. 

The  Pruning  of  Citrus  Trees  in   Cali- 
fornia. 
Fungicidal    Dusts    for   the    Control   of 
Bunt. 


CIRCULARS 

No.  No. 

70.  Observations    on    the    Status    of    Corn  166. 

Growing  in  California.  167. 

82.  The  Common  Ground  Squirrel  of  Cali-  170. 

fornia. 

87.  Alfalfa.  172. 

110.  Green  Manuring  in  California.  173. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 

fornia Soils.  174. 

113.  Correspondence  Courses  in  Agriculture.  175. 
117.  The    Selection    and    Cost    of    a    Small 

Pumping  Plant.  178. 

127.  House  Fumigation.  179. 
136.  Melilotut   indica    as    a    Green-Manure 

Crop  for  California.  182. 
144.  Oidium  or  Powdery  Mildew  of  the  Vine. 

148.   "Lungworms."  183. 

151.  Feeding  and  Management  of  Hogs.  184. 

152.  Some  Observations  on  the  Bulk  Hand-  188. 

ling  of  Grain  in  California.  190. 

155.   Bovine  Tuberculosis.  193. 

157.  Control  of  the  Pear  Scab.  198. 

159.  Agriculture  in  the  Imperial  Valley.  199. 

160.  Lettuce  Growing  in  California.  201. 

161.  Potatoes  in  California.  202. 
165.  Fundamentals   of   Sugar   Beet  Culture 

under  California  Conditions.  203. 


The   Country   Farm   Bureau. 
Feeding  Stuffs  of  Minor  Importance. 
Fertilizing  California  Soils  for  the  1918 

Crop. 
Wheat  Culture. 
The    Construction    of    the    Wood-Hoop 

Silo. 
Farm   Drainage  Methods. 
Progress  Report  on  the  Marketing  and 

Distribution  of  Milk. 
The  Packing  of  Apples  in  California. 
Factors    of    Importance    in    Producing 

Milk  of  Low  Bacterial  Count. 
Extending  the  Area  of  Irrigated  Wheat 

in  California  for  1918. 
Infectious  Abortion  in  Cows. 
A  Flock  of  Sheep  on  the  Farm. 
Lambing  Sheds. 

Agriculture  Clubs   in   California. 
A  Study  of  Farm  Labor  in  California. 
Syrup  from  Sweet  Sorghum. 
Onion  Growing  in  California. 
Helpful  Hints  to  Hog  Raisers. 
County   Organizations   for   Rural   Fire 

Control. 
Peat  as  a  Manure  Substitute. 


CIRCULARS — Continued 


No. 

205. 
206. 
208. 

209. 
210. 
212. 
214. 

215. 
217. 

218. 

219. 
224. 


228. 
230. 

232. 

233. 
234. 

235. 

236. 

237. 


Blackleg. 

Jack  Cheese. 

Summary  of  the  Annual  Reports  of  the 
Farm  Advisors  of  California. 

The  Function  of  the  Farm  Bureau. 

Suggestions  to  the  Settler  in  California. 

Salvaging  Rain-Damaged  Prunes. 

Seed  Treatment  for  the  Prevention  of 
Cereal  Smuts. 

Feeding  Dairy  Cows  in  California. 

Methods  for  Marketing  Vegetables  in 
California. 

Advanced  Registry  Testing  of  Dairy 
Cows. 

The  Present  Status  of  Alkali. 

Control  of  the  Brown  Apricot  Scale 
and  the  Italian  Pear  Scale  on  Decid- 
uous Fruit  Trees. 

Vineyard  Irrigation  in  Arid  Climates. 

Testing  Milk,  Cream,  and  Skim  Milk 
for  Butterfat. 

Harvesting  and  Handling  California 
Cherries  for  Eastern  Shipment. 

Artificial  Incubation. 

Winter  Injury  to  Young  Walnut  Trees 
during  1921-22. 

Soil  Analysis  and  Soil  and  Plant  Inter- 
relations. 

The  Common  Hawks  and  Owls  of  Cali- 
fornia from  the  Standpoint  of  the 
Rancher. 

Directions  for  the  Tanning  and  Dress- 
ing of  Furs. 


No. 

238. 
239. 

240. 

241. 

242. 
244. 
245. 
246. 

247. 
248. 

249. 
250. 

251. 


252. 
253. 
254. 

255. 

256. 
257. 
258. 
259. 


The  Apricot  in  California. 

Harvesting  and  Handling  Apricots  and 
Plums  for  Eastern  Shipment. 

Harvesting  and  Handling  Pears  for 
Eastern  Shipment. 

Harvesting  and  Handling  Peaches  for 
Eastern   Shipment. 

Poultry  Feeding. 

Central  Wire  Bracing  for  Fruit  Trees. 

Vine  Pruning  Systems. 

Desirable  Qualities  of  California  Bar- 
ley for  Export. 

Colonization  and  Rural  Development. 

Some  Common  Errors  in  Vine  Pruning 
and  Their  Remedies. 

Replacing  Missing  Vines. 

Measurement  of  Irrigation  Water  on 
the  Farm. 

Recommendations  Concerning  the  Com- 
mon Diseases  and  Parasites  of 
Poultry    in    California. 

Supports  for  Vines. 

Vineyard   Plans. 

The  Use  of  Artificial  Light  to  Increase 
Winter  Egg  Production. 

Leguminous  Plants  as  Organic  Fertil- 
izer in  California  Agriculture. 

The  Control  of  Wild  Morning  Glory. 

The  Small-Seeded  Horse  Bean. 

Thinning  Deciduous  Fruits. 

Pear  By-products. 


